剑指offer：重建二叉树

题目描述

输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回。 * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: TreeNode* reConstructBinaryTree(vector<int> pre,vector<int> vin) { if(pre.size() == 0|| vin.size() == 0) return NULL; return SearchMidPoint(pre,0,pre.size()-1,vin,0,vin.size()-1); } //找出vin里面最顶层的中点 TreeNode* SearchMidPoint(vector<int> &pre, int pstart, int pend, vector<int> &vin, int vstart, int vend) { if(pstart > pend || vstart > vend) return NULL; TreeNode* midpoint; midpoint = new TreeNode(pre[pstart]); int i; for(i=vstart; i<=vend; ++i) if(vin[i] == pre[pstart]) break; if(i > vstart) midpoint->left = SearchMidPoint(pre, pstart+1, pstart+(i-vstart), vin, vstart,i-1); if(i < vend) midpoint->right = SearchMidPoint(pre, pstart+(i-vstart)+1, pend, vin, i+1, vend); return midpoint; } };