Add week 9 solutions: pacific-atlantic-water-flow

Author: gitsunmin

pacific-atlantic-water-flow/gitsunmin.ts

@@ -0,0 +1,44 @@
+/**
+ * https://leetcode.com/problems/two-sum
+ * time complexity : O(m x m)
+ * space complexity : O(m x n)
+ */
+function pacificAtlantic(heights: number[][]): number[][] {
+    const m = heights.length;
+    const n = heights[0].length;
+    const pacific: boolean[][] = Array.from({ length: m }, () => Array(n).fill(false));
+    const atlantic: boolean[][] = Array.from({ length: m }, () => Array(n).fill(false));
+
+    const directions = [[1, 0], [-1, 0], [0, 1], [0, -1]];
+
+    function dfs(r: number, c: number, visited: boolean[][], prevHeight: number) {
+        if (r < 0 || c < 0 || r >= m || c >= n || visited[r][c] || heights[r][c] < prevHeight) {
+            return;
+        }
+        visited[r][c] = true;
+        for (const [dr, dc] of directions) {
+            dfs(r + dr, c + dc, visited, heights[r][c]);
+        }
+    }
+
+    for (let i = 0; i < m; i++) {
+        dfs(i, 0, pacific, heights[i][0]);
+        dfs(i, n - 1, atlantic, heights[i][n - 1]);
+    }
+    for (let i = 0; i < n; i++) {
+        dfs(0, i, pacific, heights[0][i]);
+        dfs(m - 1, i, atlantic, heights[m - 1][i]);
+    }
+
+    const result: number[][] = [];
+
+    for (let r = 0; r < m; r++) {
+        for (let c = 0; c < n; c++) {
+            if (pacific[r][c] && atlantic[r][c]) {
+                result.push([r, c]);
+            }
+        }
+    }
+
+    return result;
+}