1: /*
2: author:justinzhang
3: email:uestczhangchao@gmail.com
4: time:2012-8-19 9:44:46
5: des.: to left rotate a string,e.g, abcedef->cedefab
6: */
7:
8: #include <iostream>
9: #include <string>
10: using namespace std;
11:
12: void swap_str(string &str, int i, int j)
13: { 14: char c = str[i];
15: str[i] = str[j];
16: str[j] = c;
17: }
18:
19: /*
20: This routine is used to reverse a string,e.g,abcd->dcba
21: */
22: void reverse_str(string &str,int start, int end)
23: { 24: for(;start<end;start++,end--)
25: { 26: swap_str(str, start, end);
27: }
28: }
29:
30: /*
31: This routine is used to left_shift a string by offset bits,e.g.
32: left shift string abcdefg by 2 bits, we get results:cdefgab;
33: we first devide the string by two parts,AB, first we reverse A, then we
34: reverse B, the we get string A'B',finally, we reverse A'B',That's the result we want;
35: */
36: string &left_rotate_string(string &str, int offset)
37: { 38: int len = str.length();
39: cout << len << endl;
40: reverse_str(str, 0, offset-1);
41: reverse_str(str, offset, len-1);
42: reverse_str(str, 0, len-1);
43: return str;
44: }
45:
46: /*
47: This routine is used to right_shift a string by offset bits,e.g.
48: right shift string abcdefg by 2 bits, we get results:fgabcde
49: */
50: string &right_rotate_string(string &str, int offset)
51: { 52: int len = str.length();
53: reverse_str(str, 0, len-offset-1);
54: reverse_str(str, len-offset, len-1);
55: reverse_str(str, 0, len-1);
56: return str;
57: }
58:
59:
60: int main()
61: { 62: string str;
63: cin >> str;
64: str = left_rotate_string(str,2);
65: cout << str << endl;
66: str = right_rotate_string(str,2);
67: cout << str << endl;
68: return 0;
69: }
70:
71:
72:
73:
