【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/