feat: 螺旋矩阵

Author: sl1673495

递归与回溯/螺旋矩阵-54.js

@@ -0,0 +1,56 @@
+/**
+ * @param {number[][]} matrix
+ * @return {number[]}
+ */
+let spiralOrder = function (matrix) {
+  let maxY = matrix.length
+  if (!maxY) return []
+  let maxX = matrix[0].length
+
+  // 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 < maxY; y++) {
+      visited[y] = []
+  }
+  let isValid = (y, x) => {
+      return y >= 0 && y < maxY && x >= 0 && x < maxX && !visited[y][x]
+  }
+
+  let targetLength = maxY * maxX
+  let res = []
+
+  let helper = (y, x) => {
+      let val = matrix[y][x]
+      res.push(val)
+
+      if (res.length === 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)
+  }
+
+  helper(0, 0)
+
+  return res
+};