1.题目:
给定一个二叉树,返回它的中序 遍历。
示例:
输入: [1,null,2,3]
1
\
2
/
3
输出: [1,3,2]
2.代码:
//非递归法:
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* struct TreeNode *left;
* struct TreeNode *right;
* };
*/
/**
* Return an array of size *returnSize.
* Note: The returned array must be malloced, assume caller calls free().
*/
/*
栈初试化top=0;
入栈[top++]=x;
出栈x=[--top];
top指向下一个空位置;
*/
typedef struct TreeNode* Tree;
typedef struct {
Tree* array; //存放指针的数组
int top;
}Stack;
int* inorderTraversal(struct TreeNode* root, int* returnSize) {
int *r=NULL;
*returnSize=0;
Stack *s=malloc(sizeof(Stack));
s->array=(Tree*)malloc(sizeof(Tree)); //初始化
s->top=0;
while(s->top||root){
if(root){
s->array=(Tree*)realloc(s->array,sizeof(Tree)*(s->top+1));//加一个
s->array[s->top++]=root; //*******
root=root->left; //*******
}
else{
root=s->array[--s->top]; //*******
r=(int *)realloc(r,sizeof(int)*((*returnSize)+1)); //加一个
r[*returnSize]=root->val;
(*returnSize)+=1;
root=root->right; //*******
}
}
return r;
}
3.知识点:
1.中序遍历非递归法
2.栈的使用: