根据先序 中序构造二叉树

题目描述

输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回

实现代码

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {    TreeNode* solve(int pl,int pr,int vl,int vr,vector<int> pre,vector<int> vin){        TreeNode *root=NULL;        if(pl<=pr){            int k;            root= new TreeNode(pre[pl]);            for(int i=vl;i<=vr;i++){                if(vin[i] == pre[pl])                    {                    k=i;                    break;                }            }            root->left = solve(pl+1,pl+k-vl,vl,k-1,pre,vin);            root->right = solve(pl+k-vl+1,pr,k+1,vr,pre,vin);        }        return root;    }public:    TreeNode* reConstructBinaryTree(vector<int> pre,vector<int> vin) {        int pl,vl;        pl = (int)pre.size()-1;        vl = (int)vin.size()-1;        return solve(0,pl,0,vl,pre,vin);    }};