实现有 1、2、3、4 个数字，能组成多少个互不相同且无重复数字的三位数？都是多少？并且输出多少个

1、题目

实现有 1、2、3、4 个数字，能组成多少个互不相同且无重复数字的三位数？都是多少？并且输出多少个

分析： 可填在百位、十位、个位的数字都是 1、2、3、4。组成所有的排列后再去掉不满足条件的排列，多少个我们可以用数学知识很简单获得，结果是4 * 3 * 2 = 24个，结果是24个，当然我们用编程也可以。

2 、温馨提示

3、源代码实现

#include <stdio.h>

int main()
{
    int i, j, k;
    int count = 0;
    for (i = 1; i < 5; i++) /*以下为三重循环*/
        for (j = 1; j < 5; j++)
            for (k = 1; k < 5; k++)
            {
                if (i != k && i != j && j != k) /*确保 i、j、k 三位互不相同*/
                {
                    printf("%d,%d,%d\n", i, j, k);
                    printf("result is is %d\n", i * 100 + j * 10 + k);
                    ++count;
                }
            }
    printf("一共有 %d 个\n", count);
    return 0;
}

4、运行结果

1,2,3
result is is 123
1,2,4
result is is 124
1,3,2
result is is 132
1,3,4
result is is 134
1,4,2
result is is 142
1,4,3
result is is 143
2,1,3
result is is 213
2,1,4
result is is 214
2,3,1
result is is 231
2,3,4
result is is 234
2,4,1
result is is 241
2,4,3
result is is 243
3,1,2
result is is 312
3,1,4
result is is 314
3,2,1
result is is 321
3,2,4
result is is 324
3,4,1
result is is 341
3,4,2
result is is 342
4,1,2
result is is 412
4,1,3
result is is 413
4,2,1
result is is 421
4,2,3
result is is 423
4,3,1
result is is 431
4,3,2
result is is 432
一共有 24 个