【算法习作】字符串处理两例

作者：gnuhpc
出处：http://www.cnblogs.com/gnuhpc/

1.按词倒置一个句子

题目：例如”I am a student”，经处理后得到”student am a I”，限定除了一个空格外单词间没有任何其他分隔符。

解析：将整个字符串倒置后分别对每一个词进行倒置即可。

1: /*

2:  * =====================================================================================

3:  *

4:  *       Filename:  rotateString.cpp

5:  *

6:  *    Description:  rotate a string with the sequences of a word kept

7:  *

8:  *        Version:  1.0

9:  *        Created:  04/15/2011 04:28:13 PM

10:  *       Revision:  none

11:  *       Compiler:  g++

12:  *

13:  *         Author:  gnuhpc (http://blog.csdn.net/gnuhpc), warmbupt@gmail.com

14:  *

15:  * =====================================================================================

16:  */

17:

18: #include "../include/utils.h"

19:

20: void rotateString(string& target_string)

21: {

22:     size_t size = target_string.size();

23:     size_t begin = 0;

24:     size_t end   = size-1;

25:     reverseString(target_string,begin,end);

26:

27:     begin = 0;

28:     end   = 0;

29:

30:     while(end!=size)

31:     {

32:         if(target_string[end]!=' '){

33:             ++end;

34:         }

35:         else{

36:             reverseString(target_string,begin,end-1);

37:             begin = end+1;

38:             ++end;

39:         }

40:     }

41: }

42:

43: int main(int argc, char *argv[])

44: {

45:     string target_string;

46:     cout << "please tell me the string:"<<endl;

47:     getline(cin, target_string);

48:

49:     cout << target_string << endl;

50:     rotateString(target_string);

51:     cout << target_string << endl;

52: }

 

2.左旋转字符串

题目：输入：abcdefg,2  ， 输出：cdefgab ，复杂度要求：不使用额外空间存储字符串。

思路：S=abcdefg  ,   S1=ab, S2=cdefg, !S1=ba, !S2 = gfedc => !((!S1)(!S2)) 即为所求。也就是说先按欲倒置的位置将原字符串划分为两个子串，分别倒置，然后再将整个字符串倒置即可求得。

1: /*

2:  * =====================================================================================

3:  *

4:  *       Filename:  rotateString.cpp

5:  *

6:  *    Description:  rotate a string from a specific position

7:  *

8:  *        Version:  1.0

9:  *        Created:  04/15/2011 04:28:13 PM

10:  *       Revision:  none

11:  *       Compiler:  g++

12:  *

13:  *         Author:  gnuhpc (http://blog.csdn.net/gnuhpc), warmbupt@gmail.com

14:  *

15:  * =====================================================================================

16:  */

17:

18: #include "../include/utils.h"

19:

20: void rotateString(string& target_string, const size_t position)

21: {

22:     assert((position>1)&&(position<target_string.size()));

23:     int size = target_string.size();

24:     size_t A_begin = 0;

25:     size_t A_end   = position-1;

26:     size_t B_begin = position;

27:     size_t B_end   = size-1;

28:     reverseString(target_string,A_begin,A_end);

29:     reverseString(target_string,B_begin,B_end);

30:     reverseString(target_string,A_begin,B_end);

31:

32:     cout << target_string <<endl;

33: }

34:

35: int main(int argc, char *argv[])

36: {

37:     string target_string;

38:     genRandomString(target_string,10);

39:     size_t position;

40:     cout << target_string << endl;

41:     cout << "please tell me the position:"<<endl;

42:     cin >> position;

43:

44:     rotateString(target_string,position);

45: }

辅助函数reverseString为：

1: void reverseString(string &target_string, size_t begin, size_t end)

2: {

3:     while(begin<end){

4:         target_string[begin]^=target_string[end];

5:         target_string[end]^=target_string[begin];

6:         target_string[begin]^=target_string[end];

7:         ++begin;

8:         --end;

9:     }

10: }

 

作者：gnuhpc

出处：http://www.cnblogs.com/gnuhpc/