Leetcode 105 从先序与中序遍历序列构造二叉树 C++

思路：了解了先序遍历和中序遍历的遍历顺序，然后划分左右子树即可。

class Solution {
public:
    TreeNode* buildTree(vector<int>& preorder, vector<int>& inorder) {
        return buildTree(preorder,0,preorder.size()-1,inorder,0,inorder.size()-1);
    }
    TreeNode* buildTree(vector<int>&preorder,int pleft,int pright,vector<int>&inorder,int ileft,int iright)
    {
        if(pleft>pright||ileft>iright) return NULL;
        int i=0;
        for(i=ileft;i<iright;++i)
        {
            if(preorder[pleft]==inorder[i]) break;
        }
        TreeNode* cur=new TreeNode(preorder[pleft]);
        cur->left=buildTree(preorder,pleft+1,pleft+i-ileft,inorder,ileft,i-1);
        cur->right=buildTree(preorder,pleft+i-ileft+1,pright,inorder,i+1,iright);
        return cur;
    }
};