例如将“I am a student”转化为"student a am I"。

#include <stdio.h>  
#include <string.h>  
//逆转字符串
char* Reverse(char *str, int len)
{
    if(str == NULL || len <= 0)
        return str;
    char *pLast = str + len - 1;
    char *pBegin = str;
    while(pBegin < pLast)
    {   
        char temp = *pBegin;
        *pBegin = *pLast;
        *pLast = temp;
        ++ pBegin;
        -- pLast;
    }   
    return str;
}

//逆转句子
char * ReverseSentence(char *str)
{
    if(str == NULL)
    {   
        return str;
    }   
    //逆转整个句子
    Reverse(str, strlen(str));
    //逆转各个单词
    char *pBegin = str;
    char *pEnd = str;
    while(*pEnd != '\0')
    {   
        while(*pEnd != '\0' && *pEnd != ' ')
            ++pEnd;
        //逆转单词
        Reverse(pBegin, pEnd - pBegin);
        if(*pEnd == '\0')
        {
            break;
        }
        ++pEnd;
        pBegin = pEnd;
    }
    return str;
}

int main()
{
    char str1[] = "";
    char str2[] = "a";
    char str3[] = "abc";
    char str4[] = "I am a student";
    if(strcmp(ReverseSentence(str1), "") == 0
            || strcmp(ReverseSentence(str2), "a") == 0
            || strcmp(ReverseSentence(str3), "abc") == 0
            || strcmp(ReverseSentence(str4), "student a am I") == 0
            )
    {
        printf("reverse sentence ok\n");
    }
    return 0;
}