2017-7-21未命名文件

第一章 Arrays And Strings

• 1.1 Is_unique.cpp

1. #include <string>

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2. #include <vector>

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3. #include <iostream>

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4. #include <bitset>

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5. using namespace std;

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6. ---

7. bool isUniqueChars(const string &str)

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8. {

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9. if (str.length() > 128)

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10. {

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11. return false;

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12. }

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13. vector<bool> char_set(128
    );

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14. for (int i = 0; i < str.length(); i++)

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15. {

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16. int val = str[i];

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17. if (char_set[val])

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18. {

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19. return false;

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20. }

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21. char_set[val] = true;

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22. }

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23. return true;

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24. }

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25. ---

26. bool isUniqueChars_bitvector(const string &str) {

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27. //Reduce space usage by a factor of 8 using bitvector.

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28. //Each boolean otherwise occupies a size of 8 bits.

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29. bitset<256> bits(0);

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30. for(int i = 0; i < str.length(); i++) {

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31. int val = str[i];

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32. if(bits.test(val) > 0) {

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33. return false;

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34. }

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35. bits.set(val);

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36. }

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37. return true;

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38. }

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39. bool isUniqueChars_noDS(const string &str) {

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40. for(int i = 0; i < str.length()-1; i++) {

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41. for(int j = i+1; j < str.length(); j++) {

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42. if(str[i] == str[j]) {

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43. return false;

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44. }

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45. }

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46. }

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47. return true;

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48. }

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49. ---

50. int main(){

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51. vector<string> words = {"abcde", "hello", "apple", "kite", "padle"};

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52. for (auto word : words)

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53. {

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54. cout << word << string(": ") << boolalpha << isUniqueChars(word) <<endl;

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55. }

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56. cout <<endl << "Using bit vector" <<endl;

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57. for (auto word : words)

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58. {

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59. cout << word << string(": ") << boolalpha << isUniqueChars_bitvector(word) <<endl;

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60. }

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61. cout <<endl << "Using no Data Structures" <<endl;

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62. for (auto word : words)

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63. {

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64. cout << word << string(": ") << boolalpha << isUniqueChars_bitvector(word) <<endl;

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65. }

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66. return 0;

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67. }

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2017-7-21未命名文件