c - 我无法理解这段代码是如何工作的

Question

关闭。这个问题需要多问 focused 。目前不接受答案。

---

想要改进此问题吗？更新问题，使其仅关注一个问题 editing this post .

已关闭 8 年前。

Improve this question

这是一个 C 程序，用于找出单词的所有可能组合 -->

# include <stdio.h>

/* Function to swap values at two pointers */
void swap (char *x, char *y)
{
    char temp;
    temp = *x;
    *x = *y;
    *y = temp;
}

/* Function to print permutations of string
   This function takes three parameters:
   1. String
   2. Starting index of the string
   3. Ending index of the string. */
void permute(char *a, int i, int n)
{
   int j;
   if (i == n)
     printf("%s\n", a);
   else
   {
        for (j = i; j <= n; j++)
       {
          swap((a+i), (a+j));
          permute(a, i+1, n);
          swap((a+i), (a+j)); //backtrack
       }
   }
}

/* Driver program to test above functions */
int main()
{
   char a[] = "ABC"; 
   permute(a, 0, 2);
   getchar();
   return 0;
}

谁能解释一下排列代码部分是如何工作的？提前致谢

Answer 1

拿这段代码来运行它，懒得写所有阶段为什么不让计算机来做呢？

# include <stdio.h>

/* Function to swap values at two pointers */
void swap (char *x, char *y)
{
    char temp;
    printf("Swapping %c with %c\n",*x,*y); //<---------- I ADDED THIS FOR YOU
    temp = *x;
    *x = *y;
    *y = temp;
}

/* Function to print permutations of string
   This function takes three parameters:
   1. String
   2. Starting index of the string
   3. Ending index of the string. */
void permute(char *a, int i, int n)
{
   int j;
   printf("-----Now in permute(a,%d,%d)-----\n",i,n); //<---------- I ADDED THIS FOR YOU
   printf("-----String is now %s-----\n",a); //<---------- I ADDED THIS FOR YOU
   if (i == n)
     printf("%s\n", a);
   else
   {
        for (j = i; j <= n; j++)
       {
          swap((a+i), (a+j));
          permute(a, i+1, n);
          swap((a+i), (a+j)); //backtrack
       }
   }
}

/* Driver program to test above functions */
int main()
{
   char a[] = "ABC"; 
   permute(a, 0, 2);
   getchar();
   return 0;
}