[LeetCode] Construct Binary Tree from Inorder and Postorder Traversal

/**
* 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 *build(vector<int> &inorder, vector<int> &postorder, int s, int t, int p, int q) {
if (s > t || p > q) return NULL;

int pivot = postorder[q];
int v;

for (v = s; v <= t; v++) {
if (inorder[v] == pivot)
break;
}

TreeNode *parent = new TreeNode(pivot);

parent->left  = build(inorder, postorder, s, v - 1, p, p + (v - s) - 1);
parent->right = build(inorder, postorder, v + 1, t, p + (v - s), q - 1);

return parent;
}

TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
return build(inorder, postorder, 0, inorder.size() - 1, 0, postorder.size() - 1);
}
};