June 17 ques

Author: Rishabh0210

JuneLeetCodingChallenge2020/Surrounded_Regions.cpp

@@ -0,0 +1,63 @@
+//https://leetcode.com/explore/challenge/card/june-leetcoding-challenge/541/week-3-june-15th-june-21st/3363/
+
+class Solution {
+private:
+    void traverse(vector<vector<char>>& copy, vector<vector<char>>& board, vector<vector<bool>>& visited, int r, int c) {
+        visited[r][c] = true;
+        
+        int row[] = {0, 0, -1, 1};
+        int col[] = {-1, 1, 0, 0};
+        int n = board.size();
+        int m = board[0].size();
+        
+        for(int i = 0; i < 4; i++) {
+            int R = r + row[i];
+            int C = c + col[i];
+            
+            if(R >= 0 && R < n && C >= 0 && C < m && copy[R][C] == 'O' && !visited[R][C]){
+                board[R][C] = 'O';
+                traverse(copy, board, visited, R, C);
+            }
+        }
+    }
+public:
+    void solve(vector<vector<char>>& board) {
+        if(board.size() == 0)
+            return;
+        int n = board.size();
+        int m = board[0].size();
+        
+        vector<vector<char>> copy = board;
+        int i, j;
+        for(i = 1; i < n - 1; i++) {
+            for(j = 1; j < m - 1; j++) {
+                if(board[i][j] == 'O')
+                    board[i][j] = 'X';
+            }
+        }
+        
+        vector<vector<bool>> visited(board.size(), vector<bool>(board[0].size(), false));
+        
+        // for(i = 0; i < n; i++) {
+        //     for(j = 0; j < m; j++)
+        //         cout << board[i][j] << " ";
+        //     cout << endl;
+        // }
+        for(i = 0; i < m; i++) {
+            if(board[0][i] == 'O' && !visited[0][i])
+                traverse(copy, board, visited, 0, i);
+        }
+        for(i = 0; i < m; i++) {
+            if(board[n - 1][i] == 'O' && !visited[n - 1][i])
+                traverse(copy, board, visited, n - 1, i);
+        }
+        for(i = 0; i < n; i++) {
+            if(board[i][0] == 'O' && !visited[i][0])
+                traverse(copy, board, visited, i, 0);
+        }
+        for(i = 0; i < n; i++) {
+            if(board[i][m - 1] == 'O' && !visited[i][n - 1])
+                traverse(copy, board, visited, i, n - 1);
+        }
+    }
+};