[LeetCode] Construct Binary Tree from Preorder and Inorder Traversal

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Given preorder and inorder traversal of a tree, construct the binary tree.

Note: You may assume that duplicates do not exist in the tree.

/** * 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> &preorder,vector<int> &inorder) {        int len = inorder.size();        return build(preorder,0,len-1,inorder,0,len-1);    }private:    TreeNode * build(vector<int> &preorder,int begpreorder,int endpreorder,vector<int> &inorder,int begInorder,int endInorder){                if(begInorder>endInorder || begpreorder>endpreorder)            return NULL;                int val = preorder[begpreorder];        TreeNode *root = new TreeNode(val);        if(endInorder==begInorder)            return root;        int i,j=0;        for(i=begInorder;i<=endInorder;i++,j++){           if(inorder[i]==val)               break;        }                    root->left = build(preorder,begpreorder+1,begpreorder+j,inorder,begInorder,i-1);        root->right = build(preorder,begpreorder+1+j,endpreorder,inorder,i+1,endInorder);        return root;        }};