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


void conventStr(char *str, const int strlen);


int main(void)
{
    char str[] = "how old are you?";
    conventStr(str, sizeof(str));
    printf("%s", str);
    system("pause");
    //system("pause");
}



void conventStr(char *str,const int strlength)
{
    char *newStr = (char *)malloc(strlength);
    int index = strlength;
    int newStrIndex = 0;
    memset(newStr, ‘ ‘, strlength);
    for (int i = strlength - 1; i >= 0; i--)
    { 
        if ((str[i] == ‘?‘) || (str[i] == ‘\0‘))
        {
            index = i;
            newStr[i] = *(str + i);
        }
            
        if (str[i] == ‘ ‘)
        {
            memcpy(newStr + newStrIndex, str + i +1, index - i -1);//复制单词
            newStrIndex += index - i; //新的存储数组索引，指示保存到哪里了
            newStr[newStrIndex - 1] = ‘ ‘; //空格加到单词后面
            index = i;
        }
        if (i == 0)
        {
            memcpy(newStr + newStrIndex, str, index - i);//复制单词

        }
    }
    memcpy(str, newStr, strlength);
    free(newStr);
}

?