6用C语言实现.用一个函数来实现将一行字符串中最长的单词找出。此行字符串从主函数传递给该函数。

以下是用C语言实现将一行字符串中最长的单词找出的函数示例：

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

void findLongestWord(char str[]) {
    int i, j, len, maxLen = 0, start = -1;
    char longest[100], temp[100];
    len = strlen(str);
    for (i = 0; i < len; i++) {
        if ((str[i] >= 'a' && str[i] <= 'z') || (str[i] >= 'A' && str[i] <= 'Z')) {
            if (start == -1) {
                start = i;
            }
        } else {
            if (start != -1) {
                int tempLen = i - start;
                strncpy(temp, &str[start], tempLen);
                temp[tempLen] = '\0';
                if (tempLen > maxLen) {
                    maxLen = tempLen;
                    strcpy(longest, temp);
                }
                start = -1;
            }
        }
    }
    if (start != -1) {
        int tempLen = i - start;
        strncpy(temp, &str[start], tempLen);
        temp[tempLen] = '\0';
        if (tempLen > maxLen) {
            maxLen = tempLen;
            strcpy(longest, temp);
        }
    }
    printf("The longest word is: %s\n", longest);
}

int main() {
    char str[100];
    printf("Please enter a string: ");
    fgets(str, 100, stdin);
    findLongestWord(str);
    return 0;
}