[LeetCode] Construct Binary Tree from Preorder and Inorder Traversal

Given preorder and inorder traversal of a tree, construct the binary 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 *generate(vector<int> &preorder, vector<int> &inorder,int pl,int pr,int il,int ir){
        TreeNode *root;
        if(pl > pr || il > ir)
            root = NULL;
        else{
            root = new TreeNode(preorder[pl]);
            int i;
            for(i = il;i <= ir && inorder[i] != preorder[pl];i ++);
            root -> left = generate(preorder,inorder,pl + 1,pl + i - il,il,i - 1);
            root -> right = generate(preorder,inorder,pl + i - il + 1,pr,i + 1,ir);
        }
        return root;
    }
    TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
        return generate(preorder,inorder,0,preorder.size() - 1,0,inorder.size() - 1);
    }
};