c - 字符串数组排序 C

Question

我一直在尝试让这个程序按列索引对二维字符串数组进行排序。

我像这样初始化了这个二维数组:

char *str[ROWS][COLS] = {{"Russia", "Boxing", "Mens", "Gold"},
                         {"America", "Cycling", "Mens", "Gold"}, 
                         {"New Zealand", "Swimming", "Womens", "Silver"},   
                         {"India", "Badminton", "Mens", "Bronze"}};

如果我想按第一列(国家名称)对这个数组进行排序，那么它将看起来像这样:

char *str[ROWS][COLS] = {{"America", "Cycling", "Mens", "Gold"}, 
                         {"India", "Badminton", "Mens", "Bronze"}};
                         {"New Zealand", "Swimming", "Womens", "Silver"},   
                         {"Russia", "Boxing", "Mens", "Gold"}};

这是我到目前为止所做的，几乎是正确的，除了排序方法。我在实现时遇到了麻烦。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define ROWS 4
#define COLS 4

void print_array(char *str[][COLS]);
void sort_array(char *str[][COLS], int nrows, int col);

int
main(void) {
    char *str[ROWS][COLS] = {{"Russia", "Boxing", "Mens", "Gold"},
                             {"America", "Cycling", "Mens", "Gold"}, 
                             {"New Zealand", "Swimming", "Womens", "Silver"}, 
                             {"India", "Badminton", "Mens", "Bronze"}};
    int col;

    /* array before sorting */
    printf("Before: \n");
    print_array(str);

    /*choosing column index to sort by*/
    printf("\nChoose which column index you wish to sort by: ");
    if (scanf("%d", &col) != 1) {
        printf("Invalid input\n");
        exit(EXIT_FAILURE);
    }

    sort_array(str, ROWS, col);

    /* array after sorting */
    printf("\nAfter: \n");
    print_array(str);

return 0;
}

void
print_array(char *str[][COLS]) {
    int i, j;

    for (i = 0; i < ROWS; i++) {
        for (j = 0; j < COLS; j++) {
            printf("%s  ", str[i][j]);
        }
        printf("\n");
    }
}

/*function used for sorting the array */
void
sort_array(char *str[][COLS], int nrows, int col) {
    int i, j;
    char *temp;

    for (i = 0; i < nrows; i++) {
        for (j = i; j < nrows; j++) {
            if(strcmp(str[i][col], str[j][col]) > 0) {
                temp = str[i][col];
                str[i][col] = str[j][col];
                str[j][col] = temp;
            }
        }
    }   
}

我遇到的问题是我的排序算法不是交换行，而是交换该列中的字符串。我还尝试使用 insertion sort 算法，但我不确定如何使用二维字符串数组来实现它。

任何帮助将不胜感激:)

Answer 1

从 C11 开始，您可以按如下方式进行:

int compare_col(const void *a, const void *b, void *ctx) {
    int col = *(int*)ctx;
    return strcmp(((char**)a)[col], ((char**)b)[col]);
}

/*function used for sorting the array */
void sort_array(char *str[][COLS], int nrows, int col) {
    qsort_s(str, nrows, sizeof(char*)*COLS, compare_col, &col);
}