a010: 因數分解

使用試除法

#include <stdio.h>
#include <math.h>

func(int x, int *p)
{
    int prime;
    int divisor = 0;
    int dividend = x;
    int counter = 0;

    if(dividend <= 1)
    {
        printf("%d\n", dividend);
        return;
    }

    while(*p)
    {
        prime = *p++;
        while(1)
        {
            if(!(dividend % prime)) /* 可整除 */
            {
                divisor = dividend / prime;
                counter++;
                dividend = divisor;
            }
            else
            {
                if(counter)
                {
                    if(counter > 1)
                    {
                        if(dividend == 1)
                        {
                            printf("%d^%d\n", prime, counter);
                            return;
                        }
                        else
                        {
                            printf("%d^%d * ", prime, counter);
                        }
                    }
                    else
                    {
                        if(dividend == 1)
                        {
                            printf("%d\n", prime);
                            return;
                        }
                        else
                        {
                            printf("%d * ", prime);
                        }
                    }
                    counter = 0;
                    break;
                }
                else
                {
                    break;
                }
            }
        }
    }
    printf("%d\n", dividend);
}

main()
{
    int p[] = { 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71,
                         73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173,
                         179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281,
                         283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409,
                         419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541,
                         547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659,
                         661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809,
                         811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941,
                         947, 953, 967, 971, 977, 983, 991, 997, 0};
    int x;
    while(scanf("%d", &x) != EOF)
    {
        func(x, p);
    }
    return 0;
}