AcWing 828. 模拟栈

Posted 2022-02-10 MangataTS

题目连接

https://www.acwing.com/problem/content/830/

思路

我们直接开一个a数组，然后用一个整数top表示栈顶，0的时候表示为栈空，然后不断模拟就好啦

#include<bits/stdc++.h>
using namespace std;
//----------------自定义部分----------------
#define ll long long
#define mod 1000000009
#define endl "\\n"
#define PII pair<int,int>

int dx[4]=0,-1,0,1,dy[4]=-1,0,1,0;

ll ksm(ll a,ll b) 
	ll ans = 1;
	for(;b;b>>=1LL) 
		if(b & 1) ans = ans * a % mod;
		a = a * a % mod;
	
	return ans;


ll lowbit(ll x)return -x & x;

const int N = 2e6+10;
//----------------自定义部分----------------
int n,m,q,a[N],top;

int main()

	cin>>m;
	string op;
	for(int i = 1;i <= m; ++i) 
		cin>>op;
		if(op == "push")
			int x;
			cin>>x;
			a[++top] = x;
		
		else if(op == "pop")
			if(top) top--;
		
		else if(op == "empty")
			if(!top) cout<<"YES"<<endl;
			else cout<<"NO"<<endl;
		
		else if(op == "query")
			if(top) cout<<a[top]<<endl;
		
	
	
	return 0;