剑指OFFER----32-3、按之字形顺序打印二叉树(js实现)

题目

请实现一个函数按照之字形打印二叉树，即第一行按照从左到右的顺序打印，第二层按照从右至左的顺序打印，第三行按照从左到右的顺序打印，其他行以此类推。

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思路

队列按情况反转row

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function Print(pRoot) {
    // write code here
    if (!pRoot) {
        return []
    }
    let result = []
    let queue = []
    let vrse = false
    queue.push(pRoot)
    while (queue.length > 0) {
        let len = queue.length
        let row = []
        for (let i = 0; i < len; i++) {
            let shiftItem = queue.shift()
            if (shiftItem.left) {
                queue.push(shiftItem.left)
            }
            if (shiftItem.right) {
                queue.push(shiftItem.right)
            }
            row.push(shiftItem.val)
        }
        if (vrse) {
            reverse(row)
            result.push(row)
        } else {
            result.push(row)
        }
        vrse = !vrse
    }
    return result
}

function reverse(arr) {
    let i = 0
    let j = arr.length - 1
    while (i < j) {
        let temp = arr[i]
        arr[i] = arr[j]
        arr[j] = temp
        i++
        j--
    }
}