Construct Binary Tree from Preorder and Inorder Traversal

Construct Binary Tree from Preorder and Inorder Traversal

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

分析: 根据前序遍历和中序遍历构造一棵树，递归求解即可

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    void Build(int l1,int l2, int r1,int r2, const vector<int>& pre, const vector<int> & in, TreeNode*& root){
        root = new TreeNode(pre[l1]);
        int i;
        for(i=r1; i<=r2; i++)
            if(in[i]==root->val)
                break;
        if(i==r1)
            root->left=nullptr;
        else
            Build(l1+, l1+i-r1,r1, i- ,pre,in, root->left);
        if(i==r2)
            root->right=nullptr;
        else
            Build(l1+i-r1+, l2, i+, r2, pre, in, root->right);
        return;
    }
    TreeNode* buildTree(vector<int>& preorder, vector<int>& inorder) {
        if(preorder.size()== && inorder.size()==)
            return nullptr;
        TreeNode* root;
        Build(,preorder.size()-, , inorder.size()-, preorder, inorder, root);
        return root;
    }
};