add Pacific Atlantic Water Flow solution

Author: HoonDongKang

pacific-atlantic-water-flow/HoonDongKang.ts

@@ -0,0 +1,53 @@
+/**
+ * [Problem]: [417] Pacific Atlantic Water Flow
+ * (https://leetcode.com/problems/pacific-atlantic-water-flow/description/)
+ */
+function pacificAtlantic(heights: number[][]): number[][] {
+    //시간복잡도 O(n)
+    //공간복잡도 O(n)
+    const result: number[][] = [];
+    const rows = heights.length;
+    const cols = heights[0].length;
+
+    const pacificArea: boolean[][] = Array.from({ length: rows }, () => Array(cols).fill(false));
+    const atlanticArea: boolean[][] = Array.from({ length: rows }, () => Array(cols).fill(false));
+
+    function dfs(visited: boolean[][], row: number, col: number) {
+        if (row < 0 || col < 0 || row >= rows || col >= cols) return;
+        if (visited[row][col]) return;
+
+        visited[row][col] = true;
+
+        [
+            [row - 1, col],
+            [row + 1, col],
+            [row, col - 1],
+            [row, col + 1],
+        ].forEach(([r, c]) => {
+            if (r >= 0 && c >= 0 && r < rows && c < cols) {
+                if (heights[r][c] >= heights[row][col]) {
+                    dfs(visited, r, c);
+                }
+            }
+        });
+    }
+
+    for (let i = 0; i < rows; i++) {
+        dfs(pacificArea, i, 0);
+        dfs(atlanticArea, i, cols - 1);
+    }
+    for (let j = 0; j < cols; j++) {
+        dfs(pacificArea, 0, j);
+        dfs(atlanticArea, rows - 1, j);
+    }
+
+    for (let i = 0; i < rows; i++) {
+        for (let j = 0; j < cols; j++) {
+            if (pacificArea[i][j] && atlanticArea[i][j]) {
+                result.push([i, j]);
+            }
+        }
+    }
+
+    return result;
+}