C语言实现，从键盘任意输入一串字符串，每出现逗号、句号和空格那么前一个字符串标示为一个单词，统计输出这个字符串中出现了多少个单词（重复单词只记数和输出一次）

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

#define MAX_LENGTH 1000

void remove_punctuation(char *str);
int find_word(char *str, int start, int end);
int is_word_duplicate(char *word, char *words[], int count);

int main() {
    char str[MAX_LENGTH];
    char delim[] = ",. ";
    char *words[MAX_LENGTH];
    int count = 0;
    
    printf("请输入字符串：");
    fgets(str, MAX_LENGTH, stdin);
    
    remove_punctuation(str);
    
    int start = 0, end = 0;
    while (str[end] != '\0') {
        if (strchr(delim, str[end]) != NULL) {
            if (find_word(str, start, end)) {
                // 当前字符前面是单词的情况
                char *word = strndup(str + start, end - start);
                if (!is_word_duplicate(word, words, count)) {
                    words[count++] = word;
                } else {
                    free(word);
                }
            }
            start = end + 1;
        }
        end++;
    }
    
    // 处理最后一个单词
    if (find_word(str, start, end)) {
        char *word = strndup(str + start, end - start);
        if (!is_word_duplicate(word, words, count)) {
            words[count++] = word;
        } else {
            free(word);
        }
    }
    
    printf("单词数量：%d\n", count);
    printf("单词列表：\n");
    for (int i = 0; i < count; i++) {
        printf("%s\n", words[i]);
        free(words[i]);
    }
    
    return 0;
}

/**
 * 移除字符串中的标点符号
 */
void remove_punctuation(char *str) {
    int len = strlen(str);
    for (int i = 0; i < len; i++) {
        if (str[i] == ',' || str[i] == '.' || str[i] == ' ') {
            str[i] = str[i + 1];
        }
    }
}

/**
 * 判断在 str[start, end) 的范围内是否有单词
 */
int find_word(char *str, int start, int end) {
    for (int i = start; i < end; i++) {
        if (str[i] >= 'a' && str[i] <= 'z' || str[i] >= 'A' && str[i] <= 'Z') {
            return 1;
        }
    }
    return 0;
}

/**
 * 判断单词是否重复
 */
int is_word_duplicate(char *word, char *words[], int count) {
    for (int i = 0; i < count; i++) {
        if (strcmp(word, words[i]) == 0) {
            return 1;
        }
    }
    return 0;
}