[LeetCode] 1609. 奇偶树

1609. 奇偶树

解题思路

根据奇偶树的性质. 我们针对第i(奇数)层逐个元素遍历, 判断其从左至右是否严格递减 且每项为偶数 我们针对第j(偶数)层逐个元素遍历, 判断其从左至右是否严格递增 且每项为奇数 若满足上述,则符合题意. 因为逐层遍历, 故我们采取BFS最为合适.判断每层是否符合条件即可

代码

/**
 * @param {TreeNode} root
 * @return {boolean}
 */
var isEvenOddTree = function (root) {
  const isOddNum = (num) => !!(num % 2);

  let queue = [root];
  let depth = 0;
  while (queue.length) {
    const isOdd = isOddNum(depth);
    const nextQueue = [];

    let prev = queue.shift();
    if (prev.left) nextQueue.push(prev.left);
    if (prev.right) nextQueue.push(prev.right);
    if ((isOdd && isOddNum(prev.val)) || (!isOdd && !isOddNum(prev.val)))
      return false;

    for (const node of queue) {
      if (isOdd) {
        if (isOddNum(node.val)) return false;
        if (node.val >= prev.val) return false;
      } else {
        if (!isOddNum(node.val)) return false;
        if (node.val <= prev.val) return false;
      }
      if (node.left) nextQueue.push(node.left);
      if (node.right) nextQueue.push(node.right);
      prev = node;
    }
    depth++;
    queue = nextQueue;
  }
  return true;
};