LeetCode--105 从前序与中序遍历序列构造二叉树 （Construct Binary Tree from Preorder and Inorder Traversal）（C语言版）

题目描述：

代码如下：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */
struct TreeNode* BuildTree(int* preorder,int pstart,int pend,int* inorder,int istart,int iend)
{
    //判断是否需要创建节点
    if(pstart>pend||istart>iend)
        return NULL;
    struct TreeNode* root=(struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->val=preorder[pstart];
    int i=istart;
    //在中序遍历中查找当前根节点位置
    for(;i<=iend;i++){
        if(inorder[i]==preorder[pstart])
            break;
    }
    //若没有找到直接返回空
    if(i==iend+1)
        return NULL;
    //创建左节点
    root->left=BuildTree(preorder,pstart+1,pstart+i-istart,inorder,istart,i-1);
    //创建右节点
    root->right=BuildTree(preorder,pstart+i+1-istart,pend,inorder,i+1,iend);
    return root;
}
struct TreeNode* buildTree(int* preorder, int preorderSize, int* inorder, int inorderSize) {
    if(preorderSize<1||preorderSize!=inorderSize)
        return NULL;
    struct TreeNode* root=BuildTree(preorder,0,preorderSize-1,inorder,0,inorderSize-1);
    return root;   
}