Solved Problem of Day 31 (417. Pacific Atlantic Water Flow)

Author: miraehab

417. Pacific Atlantic Water Flow.cpp

@@ -0,0 +1,55 @@
+class Solution {
+public:
+    void dfs(vector<vector<int>>& h, vector<vector<bool>>& vis, int i, int j) {
+        
+        int m = h.size();
+        int n = h[0].size();
+
+        vis[i][j] = true;
+        //up
+        if (i-1 >= 0 && vis[i-1][j] != true && h[i-1][j] >= h[i][j])
+            dfs(h, vis, i-1, j);
+        //down
+        if (i+1 < m && vis[i+1][j] != true && h[i+1][j] >= h[i][j])
+            dfs(h, vis, i+1, j);
+        //left
+        if (j-1 >= 0 && vis[i][j-1] != true && h[i][j-1] >= h[i][j])
+            dfs(h, vis, i, j-1);
+        //right
+        if (j+1 < n && vis[i][j+1] != true && h[i][j+1] >= h[i][j])
+            dfs(h, vis, i, j+1);
+
+    }
+    
+    vector<vector<int>> pacificAtlantic(vector<vector<int>>& heights) {
+        
+        vector<vector<int>>ans;
+        int m = heights.size();
+        int n = heights[0].size();
+        
+        vector<vector<bool>> pacific(m, vector<bool>(n));
+        vector<vector<bool>> atlantic(m, vector<bool>(n));
+        
+        for (int i = 0; i < m; i++) {
+            
+            dfs(heights, pacific, i, 0);
+            dfs(heights, atlantic, i, n-1);
+
+        }
+        
+        for (int j = 0; j < n; j++) {
+            
+            dfs(heights, pacific, 0, j);
+            dfs(heights, atlantic, m-1, j);
+        }
+
+        
+        for (int i = 0; i < m; i++) {
+            for (int j = 0; j < n; j++) {
+                if (pacific[i][j] && atlantic[i][j]) ans.push_back({i,j});         
+            }
+        }
+        return ans;
+    }
+    
+};