PAT甲级 1051 Pop Sequence（25 分）栈模拟

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

题目大意：有个容量限制为m的栈，分别把1，2，3，…，n入栈,给出一个系列出栈顺序，问这些出栈顺序是否可能～
分析：按照要求进行模拟。先把输入的序列接收进数组vec。然后按顺序1~n把数字进栈，每进入一个数字，判断有没有超过最大范围，超过了就break。如果没超过，设index= 0，从数组的第一个数字开始，看看是否与栈顶元素相等，while相等就一直弹出栈，不相等就继续按顺序把数字压入栈～～最后根据变量index与n值是否相等输出yes或者no～ 

#include<iostream>
#include<stdio.h>
#include<stack>
#include<vector>
using namespace std;

int main(){
	int m,n,k;
	scanf("%d%d%d",&m,&n,&k);
	
	for(int i=0;i<k;i++)
	{
		vector<int> vec(n);
		stack<int> s;
		for(int j=0;j<n;j++)
			scanf("%d",&vec[j]);
		
		int index = 0;
		for(int z=1;z<=n;z++)//因为是1..m的数 
		{
			s.push(z);//注意这里是放1...m 
			if(s.size() > m)
				break;
			while(!s.empty() && s.top() == vec[index]){
				s.pop();
				index++;
			}
		}
		
		if(index == n)
			printf("YES\n");
		else
			printf("NO\n");	
	}
	
	return 0;
}