LightOJ - 1007 Mathematically Hard 欧拉函数快速打表＋前缀和

这个题 就是欧拉函数类筛法（素数的筛法打表）打表

开始各种 TLE， MLE

后来慢慢优化成 unsigned long long 后，因为输出错误还WA了一次

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<string>
#include<cmath>
#include<set>
#include<queue>
#include<stack>
#include<map>

using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int maxn = 5e6 + 7, INF = 0x7f7f7f7f, mod = 1e9 + 7;

int n, m;
ull phi[maxn];
int prim[maxn];

void get_ouler() {
    memset(phi, 0, sizeof phi);
    int id = 0;
    for(int i = 2; i < maxn; ++i) {
        if(!phi[i]) {
            phi[i] = (i-1);
            prim[id++] = i;
        }
        for(int j = 0; j < id && i*prim[j] < maxn; ++j) {
            if(i % prim[j] ) phi[i*prim[j]] = phi[i] * phi[prim[j]];
            else {
                phi[i*prim[j]] = phi[i] * prim[j];
                break;
            }
        }
    }
    phi[1] = 1;
    for(int i = 2; i < maxn; ++i) {
        phi[i] = phi[i]*phi[i] + phi[i-1];
    }
}

int main() {

    get_ouler();
    int T;
    scanf("%d", &T);
    for(int tt = 1; tt <= T; tt++) {
        int a, b;
        scanf("%d%d", &a, &b);
        printf("Case %d: %llu\n", tt, phi[b] - phi[a-1]);
    }

    return 0;
}