二叉树的最小深度

let root = {
  val: "1",
  left: {
    val: "2",
    left: null,
    right: null,
  },
  right: {
    val: "5",
    left: {
      val: "6",
      left: null,
      right: null,
    },
    right: {
      val: "7",
      left: null,
      right: null,
    },
  },
};

第一种

var minDepth = function (root) {
  if (root == null) return 0;
  if (root.left == null && root.right == null) return 1;
  //常量表示在 JavaScript 中最大的安全整数
  let nums = Number.MAX_SAFE_INTEGER;
  if (root.left != null) {
    nums = Math.min(minDepth(root.left), nums);
  }
  if (root.right != null) {
    nums = Math.min(minDepth(root.right), nums);
  }
  return nums + 1;
};

第二种

var minDepth = function (root) {
  if (!root) return 0;
  let stack = [[root, 1]];
  console.log(stack.length);
  while (stack.length) {
    let [o, n] = stack.shift();

    if (!o.left && !o.right) {
      return n;
    }
    if (o.left) stack.push([o.left, n + 1]);
    if (o.right) stack.push([o.right, n + 1]);
  }
};

console.log(minDepth(root));