用C语言

好的，以下是用C语言实现的代码：

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

#define MAX_WORD_LENGTH 50

typedef struct {
    char word[MAX_WORD_LENGTH];
    int count;
} WordCount;

int compare_word_count(const void* a, const void* b) {
    int count_a = ((WordCount*)a)->count;
    int count_b = ((WordCount*)b)->count;
    return count_b - count_a;
}

int main() {
    FILE* file = fopen("file9_1.txt", "r");
    if (file == NULL) {
        printf("Failed to open the file.\n");
        return 1;
    }

    // 统计单词出现次数
    int num_words = 0;
    WordCount* word_counts = malloc(num_words * sizeof(WordCount));
    char word[MAX_WORD_LENGTH];
    while (fscanf(file, "%s", word) == 1) {
        int found = 0;
        for (int i = 0; i < num_words; i++) {
            if (strcmp(word_counts[i].word, word) == 0) {
                word_counts[i].count++;
                found = 1;
                break;
            }
        }
        if (!found) {
            num_words++;
            word_counts = realloc(word_counts, num_words * sizeof(WordCount));
            strcpy(word_counts[num_words - 1].word, word);
            word_counts[num_words - 1].count = 1;
        }
    }

    // 按出现次数排序并输出结果
    qsort(word_counts, num_words, sizeof(WordCount), compare_word_count);
    for (int i = 0; i < num_words; i++) {
        printf("%s %d\n", word_counts[i].word, word_counts[i].count);
    }

    free(word_counts);
    fclose(file);
    return 0;
}

这个程序首先使用`fopen`函数打开文件，并使用`fscanf`函数逐个读取单词。对于每个单词，我们使用一个循环来查找它是否已经在`word_counts`数组中出现过，如果出现过，就将其计数器加1，否则就将其添加到数组中。最后，我们使用`qsort`函数按出现次数降序排序，并输出结果。

希望这个C语言程序可以帮助你解决问题！