Problem 13 Solved

JP Morgan/problem9.md

@@ -2,33 +2,29 @@
 
 ## Problem Description
 
-
 Given an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number of islands.
 
 An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.
 
-
-
 Example 1:
 
 Input: grid = [
-  ["1","1","1","1","0"],
-  ["1","1","0","1","0"],
-  ["1","1","0","0","0"],
-  ["0","0","0","0","0"]
+["1","1","1","1","0"],
+["1","1","0","1","0"],
+["1","1","0","0","0"],
+["0","0","0","0","0"]
 ]
 Output: 1
 
 Example 2:
 
 Input: grid = [
-  ["1","1","0","0","0"],
-  ["1","1","0","0","0"],
-  ["0","0","1","0","0"],
-  ["0","0","0","1","1"]
+["1","1","0","0","0"],
+["1","1","0","0","0"],
+["0","0","1","0","0"],
+["0","0","0","1","1"]
 ]
 Output: 3
-
 
 Constraints:
 
@@ -37,3 +33,49 @@ Constraints:
 - 1 <= m, n <= 300
 - grid[i][j] is '0' or '1'.
 
+/// C++ Solution
+
+class Solution {
+public:
+
+    void bfs(int row,int col,vector<vector<int>> &vis,vector<vector<char>>&grid){
+        vis[row][col]=1;
+        queue<pair<int,int>> q;
+        q.push({row,col});
+        int n = grid.size();
+        int m = grid[0].size();
+        vector<pair<int, int>> directions = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
+
+        while(!q.empty()){
+            int row = q.front().first;
+            int col = q.front().second;
+            q.pop();
+            for (auto [dr,dc] : directions){
+              int nrow = row + dr ;
+              int ncol = col + dc ;
+              if(nrow >=0  && nrow < n && ncol >= 0 && ncol <m &&
+              grid[nrow][ncol]=='1' && !vis[nrow][ncol]){
+                    vis[nrow][ncol] = 1 ;
+                    q.push({nrow,ncol}) ;
+              }
+            }
+        }
+    }
+
+    int numIslands(vector<vector<char>>& grid) {
+        int n = grid.size();
+        int m = grid[0].size();
+        vector<vector<int>>vis(n,vector<int>(m,0));
+        int count = 0 ;
+        for(int row = 0 ; row<n;row++){
+            for(int col = 0 ;col<m;col++){
+                if(!vis[row][col] && grid[row][col]=='1'){
+                    count++;
+                    bfs(row,col,vis,grid);
+                }
+            }
+        }
+        return count ;
+    }
+
+};

Microsoft/problem13.md

@@ -25,3 +25,56 @@ Constraints:
 - 1 <= s.length <= 1000
 - s consist of only digits and English letters.
 
+
+
+/// C++ Solution
+
+class Solution {
+public:
+    string longestPalindrome(string s) {
+
+     if(s.length() <= 1) return s;
+        int max_len = 1;
+        int n = s.length();
+        int st = 0, end = 0;
+
+        // Odd length
+        for(int i = 0; i < n-1; ++i){
+            int l = i, r = i;
+            while(l >= 0 && r < n){
+                if(s[l] == s[r]){
+                    l--; r++;
+                }else
+                    break;
+            }
+            int len = r-l-1;
+            if(len > max_len){
+                max_len = len;
+                st = l+1;
+                end = r-1;
+            }
+        }
+
+        // Even length
+        for(int i = 0; i < n-1; ++i){
+            int l = i, r = i+1;
+            while(l >= 0 && r < n){
+                if(s[l] == s[r]){
+                    l--; r++;
+                }else
+                    break;
+            }
+            int len = r-l-1;
+            if(len > max_len){
+                max_len = len;
+                st = l+1;
+                end = r-1;
+            }
+        }
+
+        return s.substr(st, max_len);
+
+    }
+};
+
+