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  1. #include <algorithm>
  2. #include <iostream>
  3. #include <regex>
  4. #include <string>
  5. #include <vector>
  6.  
  7. using namespace std;
  8.  
  9. enum TOKENS {
  10.     OPEN_PARENTHESIS,	
  11.     NEGATIVE_NUMBER,
  12.     NON_NEGATIVE_NUMBER,
  13.     CLOSE_PARENTHESIS,
  14.     ADDITION,
  15.     SUBTRACTION,
  16.     MULTIPLICATION,
  17.     DIVISION,
  18.     EQUALITY,
  19.     SIZE_TOKENS
  20. };
  21.  
  22. int main() {
  23. 	const auto input = "42/2 + -8\t=\n(2 + 2) * 2 * 2 -3"s;
  24. 	vector<TOKENS> tokens;
  25. 	const regex re{ "\\s*(\\(?)\\s*(-?\\s*\\d+)\\s*(\\)?)\\s*(?:(\\+)|(-)|(\\*)|(/)|(=))" };
  26.  
  27. 	for_each(sregex_iterator(cbegin(input), cend(input), re), sregex_iterator(), [&](const auto& i) {
  28. 		if(i[1].length() > 0) {
  29. 			tokens.push_back(OPEN_PARENTHESIS);
  30. 		}
  31.  
  32. 		tokens.push_back(i[2].str().front() == '-' ? NEGATIVE_NUMBER : NON_NEGATIVE_NUMBER);
  33.  
  34. 		if(i[3].length() > 0) {
  35. 			tokens.push_back(CLOSE_PARENTHESIS);
  36. 		}		
  37.  
  38. 		auto it = next(cbegin(i), 4);
  39.  
  40. 		for(int result = ADDITION; it != cend(i); ++result, ++it) {
  41. 			if (it->length() > 0U) {
  42. 				tokens.push_back(static_cast<TOKENS>(result));
  43. 				break;
  44. 			}
  45. 		}
  46. 	});
  47.  
  48. 	match_results<string::const_reverse_iterator> sm;
  49.  
  50. 	if(regex_search(crbegin(input), crend(input), sm, regex{ tokens.back() == SUBTRACTION ? "^\\s*\\d+\\s*-\\s*(-?)" : "^\\s*\\d+\\s*(-?)" })) {
  51. 		tokens.push_back(sm[1].length() == 0 ? NON_NEGATIVE_NUMBER : NEGATIVE_NUMBER);
  52. 	}
  53.  
  54. 	for (const auto& i : tokens) {
  55. 		switch (i) {
  56. 		case NEGATIVE_NUMBER:
  57. 			cout << "NEGATIVE_NUMBER\n";
  58. 			break;
  59. 		case NON_NEGATIVE_NUMBER:
  60. 			cout << "NON_NEGATIVE_NUMBER\n";
  61. 			break;
  62. 		case ADDITION:
  63. 			cout << "ADDITION\n";
  64. 			break;
  65. 		case SUBTRACTION:
  66. 			cout << "SUBTRACTION\n";
  67. 			break;
  68. 		case MULTIPLICATION:
  69. 			cout << "MULTIPLICATION\n";
  70. 			break;
  71. 		case DIVISION:
  72. 			cout << "DIVISION\n";
  73. 			break;
  74. 		case EQUALITY:
  75. 			cout << "EQUALITY\n";
  76. 			break;
  77. 		case OPEN_PARENTHESIS:
  78. 			cout << "OPEN_PARENTHESIS\n";
  79. 			break;
  80. 		case CLOSE_PARENTHESIS:
  81. 			cout << "CLOSE_PARENTHESIS\n";
  82. 		}
  83. 	}
  84. }
Success #stdin #stdout 0s 3564KB
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stdin
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Standard input is empty
stdout
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NON_NEGATIVE_NUMBER
DIVISION
NON_NEGATIVE_NUMBER
ADDITION
NEGATIVE_NUMBER
EQUALITY
OPEN_PARENTHESIS
NON_NEGATIVE_NUMBER
ADDITION
NON_NEGATIVE_NUMBER
CLOSE_PARENTHESIS
MULTIPLICATION
NON_NEGATIVE_NUMBER
MULTIPLICATION
NON_NEGATIVE_NUMBER
SUBTRACTION
NON_NEGATIVE_NUMBER
https://ideone.com/Rv5WNI
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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