Create pacific_atlantic_water_flow.cpp

Author: avidLearnerInProgress

pacific_atlantic_water_flow.cpp

@@ -0,0 +1,53 @@
+class Solution {
+public:
+    vector<vector<int>> drs{{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
+    int rows = 0;
+    int cols = 0;
+
+    void dfs(int ix, int jy, pair<int, int> prev, vector<vector<bool>> &visited, vector<vector<int>> &heights)
+    {
+        if (ix < 0 || ix >= rows || jy < 0 || jy >= cols || visited[ix][jy])
+            return;
+        if (heights[prev.first][prev.second] >heights[ix][jy])
+            return;
+
+        visited[ix][jy] = true;
+
+        for (auto &c : drs)
+        {
+            dfs(ix+c[0],jy+c[1],{ix, jy}, visited, heights);
+        }
+    }
+
+    vector<vector<int>> pacificAtlantic(vector<vector<int>> &heights)
+    {
+        rows = heights.size();
+        cols = heights[0].size();
+
+        vector<vector<bool>> pacific_drain_visited(rows, vector<bool>(cols, false));
+        vector<vector<bool>> atlantic_drain_visited(rows, vector<bool>(cols, false));
+
+        int j = 0;
+        while (j < cols) {
+            dfs(0, j, {0, j}, pacific_drain_visited, heights);
+            dfs(rows - 1, j, {rows - 1, j}, atlantic_drain_visited, heights);
+            j++;
+        }
+
+        int i = 0;
+        while (i < rows) {
+            dfs(i, 0, {i, 0}, pacific_drain_visited, heights);
+            dfs(i, cols - 1, {i, cols - 1}, atlantic_drain_visited, heights);
+            i++;
+        }
+
+        vector<vector<int>> result;
+        for (int i = 0; i < rows; i++) {
+            for (int j = 0; j < cols; j++) {
+                if (pacific_drain_visited[i][j] && atlantic_drain_visited[i][j])
+                    result.push_back({i, j});
+            }
+        }
+        return result;
+    }
+};