二叉树的构建

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) {
        int size=inorder.size();
        if(size==0){
            return NULL;
        }
        int *in=new int[size];
        int *po=new int[size];
        for(int i=0;i<size;++i){
            in[i]=inorder[i];
            po[i]=postorder[i];
        }
        return rebuild(in,po,size);
        
    }
    
    TreeNode * rebuild(int *in,int *po,int len){
        if(in==NULL||po==NULL||len==0){
            return NULL;
        }
        int llen=0;
        for(;llen<len;llen++){
            if(in[llen]==po[len-1]){
                break;
            }
        }
        int rlen=len-1-llen;
        
        TreeNode *root=new TreeNode(po[len-1]);
        root->left=rebuild(in,po,llen);
        root->right=rebuild(in+llen+1,po+llen,rlen);
        
        return root;
    }
};