字符串左移n位操作

 1 void reverse(char* str, int begin, int end)
 2 {
 3     char temp;
 4     for( ; begin < end; begin++)
 5     {
 6         temp = str[end];
 7         str[end] = str[begin];
 8         str[begin] = temp;
 9     }
10 }
11
12 void left_shift(char *str, int n, int k)
13 {
14     k=k% N;
15     reverse(str, 0, k -1);
16     reverse(str, k , n - 1);
17     reverse(str, 0, n - 1);
18 }

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