c - 如何使用 qsort 对二维矩阵的行进行排序？

Question

我的许多同事问我是否可以使用函数 qsort() 对二维数组的每一行进行排序来自 <stdlib.h>安排一个矩阵，如:

 5,  8,  7,  6,  1,  4,  3,  2, 11, 12, 10,  9, 

变成类似的东西:

 5,  6,  7,  8,  1,  2,  3,  4,  9, 10, 11, 12, 

Answer 1

问题的解决方案如下所示:

#include <stdio.h>   // scanf() printf()
#include <stdlib.h>  // qsort()

int compare (const void *a, const void *b)
{
  int x = *(int *)a;
  int y = *(int *)b;

  if (x<y) return -1; 
  if (x>y) return 1; 
  return 0;
}

int main()
{
  // Syntax of a 2D Array: array[rows][cols]
  int rows = 3, cols = 4;
  int array[3][4] = { {5,8,7,6,}, {1,4,3,2}, {11,12,10,9} };

  // Print the matrix unsorted:
  printf("\nUnsorted rows:\n");
  for (int i = 0; i < rows; i++) {
    for (int j = 0; j < cols; j++) {
      printf("%2d, ", array[i][j]);
    }
    printf("\n");
  }

  // Sort the matrix using qsort:
  for(int j = 0; j < rows; j++)
    qsort(array[j], cols, sizeof(int), compare);

  // Print the matrix sorted:
  printf("\nSorted rows:\n");
  for (int i = 0; i < rows; i++) {
    for (int j = 0; j < cols; j++) {
      printf("%2d, ", array[i][j]);
    }
    printf("\n");
  }

  return 0;
}

输出:

Unsorted rows: 5,  8,  7,  6,  1,  4,  3,  2, 11, 12, 10,  9, Sorted rows: 5,  6,  7,  8,  1,  2,  3,  4,  9, 10, 11, 12, 

感谢 flukey 在以下位置提供的有用答案: Qsorting 2d pointer arrays