[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.

/** * 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);    }};

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