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‎src/arrays.md‎

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- [Find Polygon With the Largest Perimeter](com/problems/array/FindPolygonWithTheLargestPerimeter.java)
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- [Range Sum Query 2D - Immutable](com/problems/array/RangeSumQuery2DImmutable.java)
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- [Longest Common Prefix Between Adjacent Strings After Removals](com/problems/array/LongestCommonPrefixBetweenAdjacentStringsAfterRemovals.java)
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### Sliding window

‎src/com/problems/array/LongestCommonPrefixBetweenAdjacentStringsAfterRemovals.java‎

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package com.problems.array;
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/*
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* Problem link:
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* https://leetcode.com/problems/longest-common-prefix-between-adjacent-strings-after-removals/description/
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*
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* Solution link:
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*
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* */
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import com.util.PrintUtl;
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import java.util.PriorityQueue;
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import java.util.Stack;
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// Tags: Arrays, hashing, prefix array
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public class LongestCommonPrefixBetweenAdjacentStringsAfterRemovals {
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public static void main(String[] args) {
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type1();
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type2();
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}
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// using a prefix and suffix array
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private static void type2() {
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String[] words = {"jump", "run", "run", "jump", "run"};
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int[] ans = longestCommonPrefix2(words);
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PrintUtl.print(ans);
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}
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private static int[] longestCommonPrefix2(String[] words) {
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int n = words.length;
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int[] ans = new int[n];
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int[] suffix = new int[n];
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int sMax = 0;
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int[] prefTemp = new int[n];
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for (int i = n - 1; i >= 0; i--) {
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}
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return ans;
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}
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// brute force solution
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// using priority queue
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private static void type1() {
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String[] words = {"jump", "run", "run", "jump", "run"};
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int[] ans = longestCommonPrefix1(words);
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PrintUtl.print(ans);
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}
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public static int[] longestCommonPrefix1(String[] words) {
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int n = words.length;
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PriorityQueue<Pair> pq = new PriorityQueue<>();
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for (int i = 0; i < n - 1; i++) {
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pq.add(new Pair(i, i + 1, prefix(words[i], words[i + 1])));
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}
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Stack<Pair> st = new Stack<>();
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int[] ans = new int[n];
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for (int i = 0; i < n; i++) {
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int pre = i - 1, post = i + 1;
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int max = 0;
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if (pre >= 0 && post < n) {
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max = prefix(words[pre], words[post]);
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}
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while (!pq.isEmpty()) {
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Pair p = pq.poll();
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st.push(p);
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if (p.start != i && p.end != i) {
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max = Math.max(max, p.prefix);
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break;
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}
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}
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ans[i] = max;
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while (!st.isEmpty()) pq.add(st.pop());
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}
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return ans;
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}
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public static int prefix(String a, String b) {
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int n1 = a.length();
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int n2 = b.length();
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int i1 = 0, i2 = 0;
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while (i1 < n1 && i2 < n2) {
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if (a.charAt(i1) == b.charAt(i2)) {
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i1++;
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i2++;
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} else {
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return i1;
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}
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}
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return Math.min(n1, n2);
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}
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static class Pair implements Comparable<Pair> {
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int start;
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int end;
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int prefix;
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Pair(int start, int end, int prefix) {
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this.start = start;
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this.end = end;
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this.prefix = prefix;
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}
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public int compareTo(Pair pair) {
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return Integer.compare(pair.prefix, this.prefix);
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}
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public String toString() {
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return "[" + start + "," + end + ":" + prefix + "]";
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}
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}
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}

‎src/com/problems/graph/PowerGridMaintenance.java‎

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package com.problems.graph;
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import com.util.PrintUtl;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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import java.util.TreeSet;
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/*
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* Problem link:
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* https://leetcode.com/problems/power-grid-maintenance/description/
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* Solution link:
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*
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*/
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public class PowerGridMaintenance {
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public static void main(String[] args) {
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type1();
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type2();
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}
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private static void type2() {
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}
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// Using union find to group the power stations then resolve the queries one by one
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// todo this is not the optimal solution, we can use a better approach
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private static void type1() {
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int c = 5;
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int[][] connections = {{1, 2}, {2, 3}, {3, 4}, {4, 5}};
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int[][] queries = {{1, 3}, {2, 1}, {1, 1}, {2, 2}, {1, 2}};
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int[] ans = processQueries1(c, connections, queries);
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PrintUtl.print(ans);
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}
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public static int[] processQueries1(int c, int[][] connections, int[][] queries) {
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// creating union find structure
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int[] parent = new int[c + 1];
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int[] wt = new int[c + 1];
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for (int i = 1; i <= c; i++) parent[i] = i;
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Arrays.fill(wt, 1);
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buildUnionFind(connections, parent, wt);
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TreeSet<Integer>[] powerStations = new TreeSet[c + 1];
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for (int node = 1; node <= c; node++) {
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// redoing the union find to get the parent of the node, if the path compression is not done
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int parentNode = parent[node] = parent(parent, node);
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if (powerStations[parentNode] == null) {
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TreeSet<Integer> set = new TreeSet<>();
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set.add(parentNode);
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powerStations[parentNode] = set;
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}
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powerStations[parentNode].add(node);
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}
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// even if the node is removed, we will still need to find the parent node, we will keep a copy of the parent array
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int[] copyParent = Arrays.copyOf(parent, parent.length);
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List<Integer> ans = new ArrayList<>();
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// Process each query
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for (int[] query : queries) {
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int op = query[0], node = query[1];
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int parentNode = parent[node];
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if (op == 1) {
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// copyParent[node] != -1 means it is not removed yet, so the ans will be the same node
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if (copyParent[node] != -1) {
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ans.add(node);
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} else {
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// the node is removed, we need to find the parent node
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TreeSet<Integer> set = powerStations[parentNode];
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int queryAns = !set.isEmpty() ? set.first() : -1;
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ans.add(queryAns);
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}
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} else {
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// we will remove the node from the power station and update the copyParent
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powerStations[parentNode].remove(node);
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copyParent[node] = -1;
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}
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}
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// Convert the list to an array
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return convertListToArray(ans);
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}
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private static void buildUnionFind(int[][] connections, int[] parent, int[] wt) {
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for (int[] edge : connections) {
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int x = edge[0], y = edge[1];
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int root1 = parent(parent, x);
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int root2 = parent(parent, y);
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if (root1 == root2) continue;
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if (wt[root1] >= wt[root2]) {
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wt[root1] += wt[root2];
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wt[root2] = 0;
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parent[root2] = root1;
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} else {
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wt[root2] += wt[root1];
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wt[root1] = 0;
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parent[root1] = root2;
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}
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}
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}
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private static int[] convertListToArray(List<Integer> list) {
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int[] arr = new int[list.size()];
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for (int i = 0; i < list.size(); i++) {
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arr[i] = list.get(i);
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}
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return arr;
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}
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static int parent(int[] par, int node) {
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int pt = node;
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while (pt != par[pt]) {
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pt = par[pt];
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}
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int root = pt;
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pt = node;
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while (pt != par[pt]) {
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int nextPt = par[pt];
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par[pt] = root;
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pt = nextPt;
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}
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return root;
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}
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}

‎src/com/problems/string/PartitionString.java‎

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package com.problems.string;
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import java.util.ArrayList;
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import java.util.HashSet;
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import java.util.List;
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import java.util.Set;
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/*
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* Problem link:
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* https://leetcode.com/problems/partition-string/description/
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*
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* Solution link:
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*
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*/
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// Tags: Array, String
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public class PartitionString {
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public static void main(String[] args) {
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type1();
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type2();
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}
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private static void type2() {
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}
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// brute force solution using set
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private static void type1() {
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String s = "abbccccd";
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List<String> ans = partitionString1(s);
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System.out.println(ans);
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}
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public static List<String> partitionString1(String s) {
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int n = s.length();
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Set<String> seen = new HashSet<>();
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List<String> ans = new ArrayList<>();
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int start = 0;
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for (int i = 0; i < n; i++) {
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String sub = s.substring(start, i + 1);
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if (!seen.contains(sub)) {
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seen.add(sub);
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ans.add(sub);
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start = i + 1;
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}
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}
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return ans;
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}
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}

‎src/graph.md‎

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- [Maximize the Number of Target Nodes After Connecting Trees I](com/problems/graph/MaximizeTheNumberOfTargetNodesAfterConnectingTrees1.java)
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- [Maximize the Number of Target Nodes After Connecting Trees II](com/problems/graph/MaximizeTheNumberOfTargetNodesAfterConnectingTrees2.java)
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- [Maximize Amount After Two Days of Conversions](com/problems/graph/MaximizeAmountAfterTwoDaysOfConversions.java)
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- [Properties Graph](com/problems/graph/PropertiesGraph.java)
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- [Properties Graph](com/problems/graph/PropertiesGraph.java)
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- [Power Grid Maintenance](com/problems/graph/PowerGridMaintenance.java)

‎src/index.md‎

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## My programming profiles
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- [github](https://github.com/abhishekghoshh)
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- [leetcode](https://leetcode.com/u/abhishekghoshh/)
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- [algo.monster](https://algo.monster/dashboard)
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## Projects
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‎src/strings.md‎

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- [Find the Sequence of Strings Appeared on the Screen](com/problems/string/FindTheSequenceOfStringsAppearedOnTheScreen.java)
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- [Minimum Remove to Make Valid Parentheses](com/problems/string/MinimumRemoveToMakeValidParentheses.java)
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- [Partition String](com/problems/string/PartitionString.java)
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### Advanced
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- [Rabin Karp](com/algo/string/RabinKarp.java)
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- [Z-Function](com/algo/string/ZFunction.java)

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