feat: 螺旋矩阵 II

Author: sl1673495

递归与回溯/递归矩阵-59.js

@@ -0,0 +1,54 @@
+/**
+ * @param {number} n
+ * @return {number[][]}
+ */
+let generateMatrix = function (n) {
+  // 记录一个 visited 数组
+  // 按照 右 -> 下 -> 左 -> 上 的方向不断前进
+  // 直到遇到边界或者已经访问过的元素 则切换成下一个方向
+  let dirs = [
+    [0, 1], // 右
+    [1, 0], // 下
+    [0, -1], // 左
+    [-1, 0], // 上
+  ]
+
+  let currentDirIndex = 0
+
+  let visited = []
+  for (let y = 0; y < n; y++) {
+    visited[y] = []
+  }
+  let isValid = (y, x) => {
+    return y >= 0 && y < n && x >= 0 && x < n && !visited[y][x]
+  }
+
+  let targetLength = n * n
+  let res = []
+  for (let y = 0; y < n; y++) {
+    res[y] = []
+  }
+
+  let helper = (y, x, num) => {
+    res[y][x] = num
+
+    if (num === targetLength) {
+      return res
+    }
+
+    visited[y][x] = true
+    let [diffY, diffX] = dirs[currentDirIndex % 4]
+    let nextY = y + diffY
+    let nextX = x + diffX
+    if (!isValid(nextY, nextX)) {
+      ;[diffY, diffX] = dirs[++currentDirIndex % 4]
+      nextY = y + diffY
+      nextX = x + diffX
+    }
+    helper(nextY, nextX, num + 1)
+  }
+
+  helper(0, 0, 1)
+
+  return res
+}