例如：

输入：s = “i am from beijing"

输出：”beijing form am i“

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

//i am form nanjing
//ginjnan mrof ma i
//nanjing form am i

//逆序算法(首尾互换)
void Reserve(char *s,int len)
{
    for(int i = 0;i < len / 2;i++)
    {
        char temp = s[i];
        s[i] = s[len - 1 - i];
        s[len - 1 - i] = temp;
    }
}

void Reserve2(char *s,int len)
{
    int count = 0;
    for(int i = 0;i < len;i++)
    {
        if(s[i] == ' ' || s[i] == '\0')
        {
            Reserve(s + i - count,count);
            count = 0; 
        }
        else
        {
            count++;
        }
    }
}

int main()
{
    char str[] = "i am form nanjing";
    Reserve(str,strlen(str));
    Reserve2(str,strlen(str));
    printf("%s\n",str);

    return 0;
}