Added pacificAtlanticWaterFlow solution

Author: nhistory

pacific-atlantic-water-flow/nhistory.js

@@ -0,0 +1,63 @@
+/**
+ * @param {number[][]} heights
+ * @return {number[][]}
+ */
+var pacificAtlantic = function (heights) {
+  const m = heights.length,
+    n = heights[0].length;
+  let result = [];
+
+  const pacific = new Array(m).fill(null).map(() => new Array(n).fill(false));
+  const atlantic = new Array(m).fill(null).map(() => new Array(n).fill(false));
+
+  const dir = [
+    [0, 1],
+    [1, 0],
+    [0, -1],
+    [-1, 0],
+  ];
+
+  const dfs = (i, j, ocean) => {
+    // Check visited cell
+    ocean[i][j] = true;
+
+    for (d of dir) {
+      let x = i + d[0],
+        y = j + d[1];
+      if (
+        x >= 0 &&
+        x < m &&
+        y >= 0 &&
+        y < n &&
+        !ocean[x][y] &&
+        heights[x][y] >= heights[i][j]
+      ) {
+        dfs(x, y, ocean);
+      }
+    }
+  };
+
+  // Check the cells can flow left and right edge
+  for (let i = 0; i < m; i++) {
+    dfs(i, 0, pacific);
+    dfs(i, n - 1, atlantic);
+  }
+
+  // Check the cells can flow top and bottom edge
+  for (let j = 0; j < n; j++) {
+    dfs(0, j, pacific);
+    dfs(m - 1, j, atlantic);
+  }
+
+  for (let i = 0; i < m; i++) {
+    for (let j = 0; j < n; j++) {
+      if (pacific[i][j] && atlantic[i][j]) {
+        result.push([i, j]);
+      }
+    }
+  }
+  return result;
+};
+
+// TC: O(m*n)
+// SC: O(m*n)