Merge pull request #1206 from dmzlingyin/master

添加(ACM模式如何构建二叉树.md): Go版本

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.Pop()
-        val := this.stack[len(this.stack)-1]
+    if val == 0 {
-        this.stack = this.stack[:len(this.stack)-1]
-        this.back = append(this.back, val)
-    }
-    if len(this.back) == 0 {
         return 0
     }
-    val := this.back[len(this.back)-1]
+    this.back = append(this.back, val)
     return val
 }
 

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