uva 294 - Divisors(枚举+计数)

题目连接：uva 294 - Divisors

题目大意：给出一个范围L~U，问说在该范围中因子数最多的数是多少。

解题思路：枚举L~U中的数，将数分解成质因子，利用乘法原理求总因子数。

#include <cstdio>
#include <cstring>
#include <cmath>

int countFactor (int x) {
    int ans = 1;
    int m = sqrt(x+0.5);

    for (int i = 2; i <= m; i++) {
        int c = 0;
        while (x % i == 0) {
            x /= i;
            c++;
        }

        ans *= (c + 1);
    }
    if (x > 1)
        ans *= 2;
    return ans;
}

int main () {
    int cas, L, U;
    scanf("%d", &cas);

    while (cas--) {
        scanf("%d%d", &L, &U);
        int ans = 0, id;
        for (int i = L; i <= U; i++) {
            int tmp = countFactor(i);
            if (tmp > ans) {
                ans = tmp;
                id = i;
            }
        }
        printf("Between %d and %d, %d has a maximum of %d divisors.\n", L, U, id, ans);
    }
    return 0;
}

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