字符串反转

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

/*
//解法一：
//时间复杂度为:O(K * N),
//空间复杂度: O(1)
char * Reverse(char *pStr, int len,  int size)
{
    len = len % size;//if len > size, it will be a recyle
    for (int i = size-1; i >= len; i--)
    {
        char tmp = pStr[size-1];
        for (int j = size-1; j >= 1; j--)
        {
            pStr[j] = pStr[j-1];
        }
        pStr[0] = tmp;
       // puts(pStr);
    }
    return pStr;
}
*/


//解法二：
//设src = "1234abc", dest = "abc1234"
//T = "1234", D = "abc"
//则 (T^D^)^ = DT

inline void Swap(char &lps, char &rps)
{
    char tmp = lps;
    lps = rps;
    rps = tmp;
}

void Reverse(char *pSrc, int pos, int size)
{
    char *pBegin = pSrc + pos,
         *pEnd = pSrc +  size- 1;

    while (pBegin < pEnd)
    {
        Swap(*pBegin, *pEnd);
        pBegin ++;
        pEnd --;
    }
    puts(pSrc);
}

int main()
{
    char str[] = "1234abc";
    int len = strlen(str);

    Reverse(str, 0, 4);//反转前4个字符
    Reverse(str, 4, len);//反转后三个字符
    Reverse(str, 0, len);//整体反转

    puts(str);

    return 0;
}