GitHub_collection_leetcode/src/constructBinaryTreeFromPreorderAndInorderTraversal/constructBinaryTreeFromPreorderAndInorderTraversal.cpp

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2014-10-20 11:23:39 +08:00
// Source : https://oj.leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/
// Author : Hao Chen
// Date : 2014-07-09
#include <stdio.h>
#include <vector>
#include <queue>
using namespace std;
struct TreeNode {
int val;
TreeNode *left;
TreeNode *right;
TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};
TreeNode *buildTree(vector<int>& preorder, int& preidx, vector<int>& inorder);
TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
int preidx=0;
return buildTree(preorder, preidx, inorder);
}
TreeNode *buildTree(vector<int>& preorder, int& preidx, vector<int>& inorder) {
if (preorder.size()<=0 || inorder.size()<=0 ) return NULL;
TreeNode *root = new TreeNode(preorder[preidx]);
if (inorder.size()==1){
return root;
}
int i;
for(i=0; i<inorder.size(); i++){
if (inorder[i] == preorder[preidx]){
break;
}
}
//error: not found
if (i == inorder.size()) return NULL;
if (preidx+1 >= preorder.size()){
return root;
}
vector<int> v(inorder.begin(), inorder.begin()+i);
if (v.size()>0) {
preidx++;
root->left = buildTree(preorder, preidx, v);
}
v.clear();
v.assign(inorder.begin()+i+1, inorder.end());
if (v.size()>0) {
preidx++;
root->right = buildTree(preorder, preidx, v);
}
return root;
}
void printTree_pre_order(TreeNode *root)
{
if (root == NULL){
printf("# ");
return;
}
printf("%c ", root->val );
printTree_pre_order(root->left);
printTree_pre_order(root->right);
}
void printTree_in_order(TreeNode *root)
{
if (root == NULL){
printf("# ");
return;
}
printTree_in_order(root->left);
printf("%c ", root->val );
printTree_in_order(root->right);
}
void printTree_level_order(TreeNode *root)
{
queue<TreeNode*> q;
q.push(root);
while (q.size()>0){
TreeNode* n = q.front();
q.pop();
if (n==NULL){
printf("# ");
continue;
}
printf("%c ", n->val);
q.push(n->left);
q.push(n->right);
}
printf("\n");
}
int main()
{
int pre_order[]={'F', 'B', 'A', 'D', 'C', 'E', 'G', 'I', 'H'};
int in_order[]={'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I'};
vector<int> preorder( pre_order, pre_order + 9 );
vector<int> inorder( in_order, in_order + 9 );
TreeNode* tree = buildTree(preorder, inorder);
printTree_level_order(tree);
printTree_pre_order(tree);
printf("\n");
printTree_in_order(tree);
printf("\n");
return 0;
}