字符串左移n位操作

void reverse(char* str, int begin, int end)
{
    char temp;
    for( ; begin < end; begin++)
    {
        temp = str[end];
        str[end] = str[begin];
        str[begin] = temp;
    }
}

void left_shift(char *str, int n, int k)
{
    k=k% N;
    reverse(str, 0, k -1);
    reverse(str, k , n - 1);
    reverse(str, 0, n - 1);
}

先把前n个字符串反转，再把后面的反转。最后再把整个字符串反转