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[UVA] 10539 - Almost Prime Numbers

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Problem A
Almost Prime Numbers
Time Limit: 1 second

Almost prime numbers are the non-prime numbers which are divisible by only a single prime number. In this problem your job is to write a program which finds out the number of almost prime numbers within a certain range.

Input
First line of the input file contains an integer N (N <= 600) which indicates how many sets of inputs are there. Each of the next N lines make a single set of input. Each set contains two integer numbers low and high (0 < low <= high < 1012).

Output
For each line of input except the first line you should produce one line of output. This line contains a single integer, which indicates how many almost prime numbers are within the range (inclusive) low…high.

Sample Input Sample Output
3
1 10
1 20
1 5
3
4
1


Problemsetter: Shahriar Manzoor, special thanks to Derek Kisman

懶得二分了

#include <stdio.h>
#include <algorithm>
#define maxN 1000000000000LLU
#define maxL (1000000>>5)+1
using namespace std;
int p[80000], pt = 0;
int mark[maxL];
int GET(int x) {    return mark[x>>5]>>(x&31)&1;}
void SET(int x) {    mark[x>>5] |= 1<<(x&31);}
void sieve() {
    int i, j, k;
    int n = 1000000;
    for(i = 2; i <= n; i++) {
        if(!GET(i)) {
            for(k = n/i, j = i*k; k >= i; k--, j -= i)
                SET(j);
            p[pt++] = i;
        }
    }
}
long long APN[160000];
int at = 0;
void build() {
    int i;
    for(i = 0; i < pt; i++) {
        long long tmp = (long long)p[i]*p[i];
        while(tmp <= maxN) {
            APN[at++] = tmp;
            tmp = tmp*p[i];
        }
    }
}
int main() {
    sieve();
    build();
    int t;
    long long a, b;
    sort(APN, APN+at);
    scanf("%d", &t);
    while(t--) {
        scanf("%lld %lld", &a, &b);
        int cnt = 0, i;
        for(i = 0; i < at; i++)
            if(a <= APN[i] && APN[i] <= b)
                cnt++;
        printf("%d\n", cnt);
    }
    return 0;
}

台長: Morris
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