1051 Pop Sequence (25分) 我的代码+别人的代码

1051 Pop Sequence (25分)

Given a stack which can keep M numbers at most. Push N numbers in the order of 1, 2, 3, ..., N and pop randomly. You are supposed to tell if a given sequence of numbers is a possible pop sequence of the stack. For example, if M is 5 and N is 7, we can obtain 1, 2, 3, 4, 5, 6, 7 from the stack, but not 3, 2, 1, 7, 5, 6, 4.

Input Specification:

Each input file contains one test case. For each case, the first line contains 3 numbers (all no more than 1000): M (the maximum capacity of the stack), N (the length of push sequence), and K (the number of pop sequences to be checked). Then K lines follow, each contains a pop sequence of N numbers. All the numbers in a line are separated by a space.

Output Specification:

For each pop sequence, print in one line "YES" if it is indeed a possible pop sequence of the stack, or "NO" if not.

Sample Input:

5 7 5
1 2 3 4 5 6 7
3 2 1 7 5 6 4
7 6 5 4 3 2 1
5 6 4 3 7 2 1
1 7 6 5 4 3 2

Sample Output:

YES
NO
NO
YES
NO

我的代码：

我的思路：用栈和队列来模拟

队列存输入的出栈顺序。栈初始为空。

n个要进栈的元素从1到n遍历一遍：

               （1）将当前元素入栈。

               （2）判断栈顶元素和队列首元素是否相等，如果相等，栈顶元素出栈，队列首元素出队

                    （2）这个地方这样写：

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	while(a.top()==s.front()&&!a.empty())
	    	{
	    	        a.pop();
	    		s.pop();
	    		if(a.empty())
	    		break;
	    		if(a.size()>=m)
	    		break;
		}

因为判断栈顶元素时，栈有可能为空，所以里面要加一个是否为空的判断，还有就是栈容量的判断，是>=,而非==。

最后，再判断栈是否为空，空则YES，反之NO。

#include<iostream>
#include<queue>
#include<algorithm>
#include<stack>
using namespace std;
int main()
{
	queue<int> s;
	stack<int> a;
	while(!a.empty())
	{
		a.pop();
	}
    while(!s.empty())
    {
    	s.pop();
	}
	int m,n,k,i,j,t;
	cin>>m>>n>>k;
	for(i=0;i<k;i++)
	{
		while(!a.empty())
		{
			a.pop();
		}
	    while(!s.empty())
	    {
	    	s.pop();
		}
		for(j=0;j<n;j++)
		{
			cin>>t;
			s.push(t);
		}
	    for(j=1;j<=n;j++)
	    {
	    	
	    	a.push(j);
//			cout<<j<<endl;
//	    	cout<<a.top()<<"  "<<s.front()<<endl;
	    	while(a.top()==s.front()&&!a.empty())
	    	{
	    		a.pop();
	    		s.pop();
	    		if(a.empty())
	    		break;
	    		if(a.size()>=m)
	    		break;
			}
			
		}
		if(!a.empty())
		cout<<"NO"<<endl;
		else
		cout<<"YES"<<endl;
	}
	return 0;
}

别人的代码：

#include<bits/stdc++.h>
using namespace std;
stack<int>st;
int digit[1005];
int main() 
{
    int n, m ,t;
    cin>> m >>n >>t;
    while(t--)
    {
    	while(!st.empty())
    		st.pop();
    	for(int i = 1; i <= n; i++)
    		scanf("%d",&digit[i]);
    	int cnt = 1;
    	int flag = 1;
		for(int i = 1; i <= n; i++)
    	{
    		st.push(i);
    		if(st.size() > m){
    			flag = 0;
    			break; //表示当前已经大于了 
			}
    		while(!st.empty() && st.top() == digit[cnt]) 
    		{
    			st.pop();
    			cnt++;
			}
		}
		if(st.empty() && flag)
			cout<<"YES"<<endl;
		else 
			cout<<"NO"<<endl;
	}
    return 0;
}

不建议用万能头文件！