cf 283A

不能简单模拟（会超时）运用一点小技巧减少时间复杂度

#include <cstdio>

#include <cstring>

using namespace std;

int a[200010];

int cc[200010];

int main()

{

    int t,n,m,tt;

    scanf("%d",&t);

    memset(cc, 0, sizeof(cc));

    memset(a, 0 ,sizeof(a));

    int top = 1;

    double sum = 0;

    while(t--)

    {

        scanf("%d",&tt);

        if(tt == 1)

        {

            scanf("%d%d",&n,&m);

            cc[n] += m;

            sum += n*m;

        }

        else if(tt == 2)

        {

            scanf("%d",&n);

            a[++top] = n;

            sum += n;

        }

        else

        {

            cc[top-1] += cc[top];

            sum -= (a[top]+cc[top]);

            cc[top] = 0;

            top--;

        }

        printf("%.6lf\n",sum/top);

    }

}

巴特西

cf 283A

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