Wins the offer - 67 string left rotation

Title Description

There is a shift in the assembly language instruction called a rotate left (the ROL), and now there is a simple task, this instruction is simulated by the string operation result. For a given character sequence S, you put its left circle after K-bit serial output. For example, the character sequence S = "abcXYZdef", rotated left required output result after three, i.e. "XYZdefabc". Is not it simple? OK, get it!

 

answer:

　　Flip to the last:

　　　　Flip the left part and right part of the flip, then flip the whole can.

 

 1 class Solution02 {
 2 public:
 3     string LeftRotateString(string str, int n) {
 4         int size = str.length();
 5         if (size < 2 || n % size == 0)return str;
 6         n %= size;
 7         Reverse(str, 0, n - 1);
 8         Reverse(str, n, size - 1);
 9         Reverse(str, 0, size - 1);
10         return str;
11     }
12 private:
13     void Reverse(string &str,int L, int R)
14     {
15         while (L < R) {
16             swap(str[L], str[R]);
17             ++L, --R;
18         }
19     }
20 };