leetcode-Construct Binary Tree from Preorder and Inorder Traversal

recursive

#include <iostream>
#include <vector>
using namespace std;

struct TreeNode {
     int val;
     TreeNode *left;
     TreeNode *right;
     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 };

class Solution {
public:
    typedef vector<int>::iterator Iter;
    TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
        return buildTreeRecur(inorder.begin(),inorder.end(),preorder.begin(),preorder.end());
    }
    TreeNode* buildTreeRecur(Iter istart,Iter iend,Iter pstart,Iter pend)
    {
        if (istart == iend) return NULL;
        int rootval = *pstart;
        Iter iterroot = find(istart,iend,rootval);
        TreeNode *res = new TreeNode(rootval);//建立根节点
        res->left = buildTreeRecur(istart,iterroot,pstart+1,pstart+1+(iterroot-istart));
        res->right = buildTreeRecur(iterroot+1,iend,pstart+1+(iterroot-istart),pend);//vector的end是最后元素还要再下一个！
        return res;
    }
};

void inorderTraversal(TreeNode* root)
{
    if (root == nullptr) return;
    inorderTraversal(root->left);
    cout << root->val << " ";
    inorderTraversal(root->right);
}
void preorderTraversal(TreeNode* root)
{
    if (root == nullptr) return;
    cout << root->val << " ";
    preorderTraversal(root->left);
    preorderTraversal(root->right);
}
int main()
{
    Solution s;
    vector<int> inorder = {2,4,1,5,3};
    vector<int> preorder = { 1,2, 4,3, 5};
    TreeNode* root = s.buildTree(preorder,inorder);
    inorderTraversal(root);
    cout << endl;
    preorderTraversal(root);
    return 0;
}