题解

直接前缀最大值
不懂就问，空库怎么出的，这日志怕不是伪造的（

#include <iostream>
#include <cstdio>
using namespace std;
int a[200005], ct;
int read(){
	char c = getchar();
	int x = 0;
	while(!isdigit(c)){
		c = getchar();
	}
	while(isdigit(c)){
		x = (x << 3) + (x << 1) + c - '0';
		c = getchar();
	}
	return x;
}
int main(){
	int t = read(), k, tmp;
	while(t--){
		k = read();
		if(k == 0){
			tmp = read();
			a[ct + 1] = max(a[ct], tmp);
			ct++;
		}
		if(k == 1) if(ct) a[ct--] = 0;
		if(k == 2) cout << a[ct] << endl;
	}

	return 0;
}