[leetcode]Construct Binary Tree from Preorder and Inorder Traversal
struct TreeNode { int val; TreeNode *left; TreeNode *right; TreeNode(int x) : val(x), left(NULL), right(NULL) {} }; class Solution { public: TreeNode *buildTree(vector<int> &pre, int preStart, vector<int> &in, int inStart, int len){ if (preStart<0 || preStart+len>pre.size() || inStart<0 || inStart+len>in.size() || len<1) return NULL; TreeNode *root = new TreeNode(pre[preStart]); int i = 0; for (i = 0; i < len; i++) if (in[inStart + i] == root->val) break; int leftLen = i; int rightLen = len - 1 - leftLen; root->left = buildTree(pre, preStart+1, in, inStart, leftLen); root->right = buildTree(pre, preStart+1+leftLen, in, inStart+leftLen+1, rightLen); return root; } TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) { // Start typing your C/C++ solution below // DO NOT write int main() function if (preorder.size() != inorder.size() || preorder.size()<1) return NULL; return buildTree(preorder, 0, inorder, 0, inorder.size()); } };
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