二叉树层次遍历

参考：https://blog.csdn.net/hansionz/article/details/81947834

二叉树的基础操作总结
https://blog.csdn.net/hansionz/article/details/81908134
队列的基础操作总结
https://blog.csdn.net/hansionz/article/details/81636644

层次遍历

层次遍历，就是从上到下一层一层的遍历
例如：

---

思路：

#include <queue>
#include <iostream>

using namespace std;

struct Treenode
{
    int val;
    Treenode *left;
    Treenode *right;
};

typedef Treenode * binTree;


void levelTraverse(binTree root)
{
    queue<binTree> q;

    q.push(root);

    if (root == NULL) return ;

    while (!q.empty())
    {
        int n = q.size();

        for (int i = 0;i<n;i++)
        {
            binTree cur = q.front();
            q.pop();
            cout<<cur->val<<endl;
            if (cur->left != NULL) q.push(cur->left);
            if (cur->right != NULL) q.push(cur->right);
        }
    }
}

void insertNode(binTree *root, int val)
{
    binTree node = (binTree)malloc(sizeof(Treenode));
    node->val = val;
    node->left= NULL;
    node->right=NULL;

    if (*root == NULL)
    {
        *root = node;
    }
    else
    {        
        if (val < (*root)->val) insertNode(&(*root)->left, val);
        else insertNode(&(*root)->right, val);
    }
}

int _tmain(int argc, _TCHAR* argv[])
{
    int nodes[] = {3,9,20,15,7};
    int len = 5;
    binTree root = NULL;
    for (int i = 0;i<len;i++)
    {
        insertNode(&root, nodes[i]);
    }
    levelTraverse(root);

    getchar();

    return 0;
}