ABC298D双端队列维护取余的值

#include <stdio.h>
const int N=600005, mo=998244353;
int n, m, i, j, k, x, y, l, r, a[N], b[N];
int main(){
    scanf("%d", &m);
    for(a[0]=i=1; i<=m; i++){
        a[i] = a[i-1]*10ll % mo;
    }
    x = l = r = b[1] = 1;
    while(m--){
        scanf("%d", &k);
        if(k == 1){
            scanf("%d", &y);
            x = (x*10ll + y) % mo;
            n++, b[++r] = y;//增加1位
        }
        else if(k == 2){
            x = (x-1ll*a[n]*b[l]) % mo + mo;//该位是b[l]*10^n
            n--, l++;//删除1位
        }
        else printf("%d\n", x%mo);
    }
    return 0;
}