diff --git a/problems/0232.用栈实现队列.md b/problems/0232.用栈实现队列.md index b00ffd80..1a56d9f3 100644 --- a/problems/0232.用栈实现队列.md +++ b/problems/0232.用栈实现队列.md @@ -275,15 +275,11 @@ func (this *MyQueue) Pop() int { /** Get the front element. */ func (this *MyQueue) Peek() int { - for len(this.stack) != 0 { - val := this.stack[len(this.stack)-1] - this.stack = this.stack[:len(this.stack)-1] - this.back = append(this.back, val) - } - if len(this.back) == 0 { + val := this.Pop() + if val == 0 { return 0 } - val := this.back[len(this.back)-1] + this.back = append(this.back, val) return val } diff --git a/problems/前序/ACM模式如何构建二叉树.md b/problems/前序/ACM模式如何构建二叉树.md index bd2e9780..444f0071 100644 --- a/problems/前序/ACM模式如何构建二叉树.md +++ b/problems/前序/ACM模式如何构建二叉树.md @@ -220,6 +220,73 @@ int main() { ## Go ```Go +package main + +import "fmt" + +type TreeNode struct { + Val int + Left *TreeNode + Right *TreeNode +} + +func constructBinaryTree(array []int) *TreeNode { + var root *TreeNode + nodes := make([]*TreeNode, len(array)) + + // 初始化二叉树节点 + for i := 0; i < len(nodes); i++ { + var node *TreeNode + if array[i] != -1 { + node = &TreeNode{Val: array[i]} + } + nodes[i] = node + if i == 0 { + root = node + } + } + // 串联节点 + for i := 0; i*2+2 < len(array); i++ { + if nodes[i] != nil { + nodes[i].Left = nodes[i*2+1] + nodes[i].Right = nodes[i*2+2] + } + } + return root +} + +func printBinaryTree(root *TreeNode, n int) { + var queue []*TreeNode + if root != nil { + queue = append(queue, root) + } + + result := []int{} + for len(queue) > 0 { + for j := 0; j < len(queue); j++ { + node := queue[j] + if node != nil { + result = append(result, node.Val) + queue = append(queue, node.Left) + queue = append(queue, node.Right) + } else { + result = append(result, -1) + } + } + // 清除队列中的本层节点, 进入下一层遍历 + queue = queue[len(queue):] + } + + // 参数n控制输出值数量, 否则二叉树最后一层叶子节点的孩子节点也会被打印(但是这些孩子节点是不存在的). + fmt.Println(result[:n]) +} + +func main() { + array := []int{4, 1, 6, 0, 2, 5, 7, -1, -1, -1, 3, -1, -1, -1, 8} + root := constructBinaryTree(array) + printBinaryTree(root, len(array)) +} + ``` ## JavaScript