LeetCode: Construct Binary Tree from Inorder and Postorder Traversal

思路：后序数组用来确定根节点的值和在数中的位置，中序数组用来确定左右子树的大小。代码细节参考了《剑指offer》一书中给的code，注意截断序列的时候不要分错。

class Solution {public:    TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) {TreeNode * root;int len = postorder.size();if(len < 1)return NULL;elseroot = constructTree(inorder.begin(),inorder.end()-1,postorder.begin(),postorder.end()-1);return root;    }TreeNode * constructTree(vector<int>::iterator in_itbegin, vector<int>::iterator in_itend, vector<int>::iterator post_itbegin, vector<int>::iterator post_itend){int v = *post_itend;TreeNode * root = new TreeNode(v);vector<int>::iterator p;for(p=in_itbegin; p<= in_itend;p++)if(*p == v)break;int leftlengh = p - in_itbegin, right_lengh = in_itend - p;if(leftlengh>0)root->left = constructTree(in_itbegin,p-1,post_itbegin,post_itend-right_lengh-1);if(right_lengh>0)root->right = constructTree(p+1,in_itend,post_itend-right_lengh+1,post_itend-1);return root;}};