competitive-programming/solved-lightOj/1197.cpp at master · the-redback/competitive-programming · GitHub

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/**
 *                                   ____
 *       ____ ___  ____ ________  __/ __/
 *      / __ `__ \/ __ `/ ___/ / / / /_
 *     / / / / / / /_/ / /  / /_/ / __/
 *    /_/ /_/ /_/\__,_/_/   \__,_/_/
 *
 *    @link : https://the-redback.com
 */

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long llu;

#define ft           first
#define sd           second
#define mp           make_pair
#define pb(x)        push_back(x)
#define all(x)       x.begin(), x.end()
#define allr(x)      x.rbegin(), x.rend()
#define mem(a, b)    memset(a, b, sizeof(a))
#define repv(i, a)   for (i = 0; i < (ll)a.size(); i++)
#define revv(i, a)   for (i = (ll)a.size() - 1; i >= 0; i--)
#define rep(i, a, b) for (i = a; i <= b; i++)
#define rev(i, a, b) for (i = a; i >= b; i--)
#define sf(a)        scanf("%lld", &a)
#define sf2(a, b)    scanf("%lld %lld", &a, &b)
#define sf3(a, b, c) scanf("%lld %lld %lld", &a, &b, &c)
#define inf          1e9
#define eps          1e-9
#define mod          1000000007
#define NN           100010

// clang-format off
#ifdef  redback
#define bug printf("line=%d\n",__LINE__);
#define debug(args...) {cout<<":: "; dbg,args; cerr<<endl;}
struct  debugger{template<typename T>debugger& operator ,(const T& v){cerr<<v<<" ";return *this;}}dbg;
#else
#define bug
#define debug(args...)
#endif  //debugging macros
// clang-format on

#define MAX 46656
#define LMT 216
#define LEN 4830
#define RNG 100032

unsigned base[MAX / 64], segment[RNG / 64], primes[LEN];

#define sq(x)      ((x) * (x))
#define mset(x, v) memset(x, v, sizeof(x))
#define chkC(x, n) (x[n >> 6] & (1 << ((n >> 1) & 31)))
#define setC(x, n) (x[n >> 6] |= (1 << ((n >> 1) & 31)))

/* Generates all the necessary prime numbers and marks them in base[]*/
void sieve() {
    unsigned i, j, k;
    for (i = 3; i < LMT; i += 2)
        if (!chkC(base, i))
            for (j = i * i, k = i << 1; j < MAX; j += k) setC(base, j);
    for (i = 3, j = 0; i < MAX; i += 2)
        if (!chkC(base, i)) primes[j++] = i;
}

/* Returns the prime-count within range [a,b] and marks them in segment[] */
int segmented_sieve(int a, int b) {
    unsigned i, j, k, cnt = (a <= 2 && 2 <= b) ? 1 : 0;
    if (b < 2) return 0;
    if (a < 3) a = 3;
    if (a % 2 == 0) a++;
    mset(segment, 0);
    for (i = 0; sq(primes[i]) <= b; i++) {
        j = primes[i] * ((a + primes[i] - 1) / primes[i]);
        if (j % 2 == 0) j += primes[i];
        for (k = primes[i] << 1; j <= b; j += k)
            if (j != primes[i]) setC(segment, (j - a));
    }
    for (i = 0; i <= b - a; i += 2)
        if (!chkC(segment, i)) cnt++;
    return cnt;
}

int main() {
// ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef redback
    freopen("C:\\Users\\Maruf\\Desktop\\in.txt", "r", stdin);
#endif

    sieve();

    ll t = 1, tc;
    sf(tc);
    ll l, m, n;
    while (tc--) {
        ll i, j, k;

        sf2(n, m);
        ll ans = segmented_sieve(n, m);

        printf("Case %lld: %lld\n", t++, ans);
    }
    return 0;
}