judge5-2.c

#include <stdio.h>
//計算階乘
int factorial(int x) {
    int i, result = 1;;
    for (i = 2; i <= x; i++) {
        result *= i;
    }
    return result;
}
//判定是否為質數
int isPrime(int x) {
    int i;
    for ( i = 2; i < x; i++ ) {
        if ( x % i == 0 )
            return 0;
    }
    return 1;
}
//做質因數分解
void factor(int x, int a[]) {
    int i = 0, count = 0;
    //最後除完為 1
    while ( x > 1 ) {
        //計算這個質數可以被整除幾次
        while ( x % a[i] == 0 ) {
            x /= a[i];
            count ++;
        }
        //算好印出，計數器歸零，陣列推進一格
        printf("%d, ", count);
        count = 0;
        i++;
    }
    printf("\n");
}
//取得質數陣列
//會得到 arr[] = {2, 3, 5, 7, 11, 13....};
void getFactor(int arr[], int size) {
    int i, x = 2;
    for (i = 0; i < size; i++) {
        while (!isPrime(x)) {
            x++;
        }
        arr[i] = x;
        x++;
    }
}

int main() {
    //size可以自訂，此處取到前500個質數
    int n, p, i, j, primeArraySize = 500;
    scanf("%d", &n);
    p = factorial(n);
    printf("%d! = %d\n", n, p);
    int prime[primeArraySize];
    getFactor(prime, primeArraySize);
    factor(p, prime);
    return 0;
}