标签：注意 end span 不能 public class space des inpu
Given a tree, you are supposed to tell if it is a complete binary tree.
Input Specification:
Each input file contains one test case. For each case, the first line gives a positive integer N (<=20) which is the total number of nodes in the tree -- and hence the nodes are numbered from 0 to N-1. Then N lines follow, each corresponds to a node, and gives the indices of the left and right children of the node. If the child does not exist, a "-" will be put at the position. Any pair of children are separated by a space.
Output Specification:
For each case, print in one line "YES" and the index of the last node if the tree is a complete binary tree, or "NO" and the index of the root if not. There must be exactly one space separating the word and the number.
Sample Input 1:9 7 8 - - - - - - 0 1 2 3 4 5 - - - -Sample Output 1:
YES 8Sample Input 2:
8 - - 4 5 0 6 - - 2 3 - 7 - - - -Sample Output 2:
NO 1
思路
判断一棵二叉树是不是完全二叉树。
层次遍历二叉树,当遍历到"-"节点时（表示空节点），检查树的节点数N和遍历次数cnt是否相等，相等yes，不想等no。
注意：输入用string而不用char，因为char不能表示两位数以上的数字。之前没注意导致代码只有部分ac。
代码
#include<iostream>
#include<vector>
#include<queue>
using namespace std;
class Node
{
public:
int left;
int right;
};
int main()
{
int N;
while(cin >> N)
{
vector<Node> nodes(N);
vector<bool> isroot(N,true);
//Build tree
for(int i = 0;i < N;i++)
{
string left,right;
cin >> left >> right;
if(left == "-")
nodes[i].left = -1;
else
{
nodes[i].left = stoi(left);
isroot[nodes[i].left] = false;
}
if(right == "-")
nodes[i].right = -1;
else
{
nodes[i].right = stoi(right);
isroot[nodes[i].right] = false;
}
}
//Find root
int root = -1;
for(int i = 0;i < isroot.size();i++)
{
if(isroot[i])
{
root = i;
break;
}
}
//BFS
queue<int> q;
q.push(root);
int cnt = 0,lastindex = -1;
while(!q.empty())
{
int tmp = q.front();
q.pop();
if(tmp == -1)
{
break;
}
cnt++;
lastindex = tmp;
q.push(nodes[tmp].left);
q.push(nodes[tmp].right);
}
//Output
if(cnt == N)
cout << "YES" << " " << lastindex <<endl;
else
cout << "NO" << " " << root << endl;
}
}
标签：注意 end span 不能 public class space des inpu
原文地址：http://www.cnblogs.com/0kk470/p/7784384.html
