Create 21 May | 934. Shortest Bridge.cpp

21 May | 934. Shortest Bridge.cpp

@@ -0,0 +1,61 @@
+class Solution {
+public:
+
+    vector<vector<int>> dir = {{0,1}, {0,-1}, {1,0}, {-1, 0}};
+
+    void dfs(vector<vector<int>>& grid, int x, int y, queue<pair<int, int>>& q){
+        int n = grid.size();
+        grid[x][y] = 2;
+        q.push({x,y});
+
+        for(auto d : dir){
+            int newX = x + d[0];
+            int newY = y + d[1];
+
+            if(newX >= 0 && newX < n && newY >= 0 && newY < n && grid[newX][newY] == 1){
+                dfs(grid, newX, newY, q);
+            }
+        }
+    }
+
+    int shortestBridge(vector<vector<int>>& grid) {
+        int n = grid.size();
+        int firstX = -1, firstY = -1;
+
+        for(int i = 0; i < n; i++){
+            for(int j = 0; j < n; j++){
+                if(grid[i][j] == 1){
+                    firstX = i;
+                    firstY = j;
+                    break;
+                }
+            }
+        }
+        queue<pair<int, int>>q;
+        dfs(grid, firstX, firstY, q);
+        int dist = 0;
+
+        while(!q.empty()){
+            int sz = q.size();
+
+            while(sz--){
+                int currX = q.front().first, currY = q.front().second;
+                q.pop();
+
+                for(auto d: dir){
+                    int newX = currX + d[0];
+                    int newY = currY + d[1];
+                    if(newX >= 0 && newX < n && newY >= 0 && newY < n && grid[newX][newY] == 1){
+                        return dist;
+                    }
+                    else if(newX >= 0 && newX < n && newY >= 0 && newY < n && grid[newX][newY] == 0){
+                        grid[newX][newY] = -1;
+                        q.push({newX, newY});
+                    }
+                }
+            }
+            dist++;
+        }
+        return dist;
+    }
+};