c++：栈的应用之表达式求值

 Stack.hpp

1. #pragma once

2. 
   

3. template <class T>

4. class Stack{

5. private:

6. T* _array;

7. size_t _capacity;

8. int _topindex;

9. public:

10. Stack()          //构造函数

11. :_array(0)

12. , _capacity(0)

13. , _topindex(-1)

14. {}

15. void Push(const T& x){                         //入栈操作

16. if (_topindex + 1 == _capacity){

17. _capacity = 2 * _capacity + 3;

18. T* tmp = new T[_capacity];

19. if (tmp == NULL){

20. cout << "failed new" << endl;

21. exit(-1);

22. }

23. memcpy(tmp, _array, sizeof(T) * (_topindex + 1));

24. delete _array;

25. _array = tmp;

26. }

27. _array[++_topindex] = x;

28. }

29. void Pop(){                                      //出栈

30. if (_topindex > -1){

31. //cout << _array[_topindex] << endl;

32. _topindex--;

33. }

34. } 

35. bool empty(){                  //清空

36. return _topindex = -1;

37. }

38. const T& top(){                             //取栈顶元素

39. //cout << _array[_topindex] << endl;

40. return _array[_topindex];

41. }

42. };

43. 
    

44. main.cpp

45. #include<iostream>

46. #include<string>

47. #include"Stack.hpp"

48. using namespace std;

49. 
    

50. enum Type{
    

51. ADD,

52. SUB,

53. MUL,

54. DIV,

55. OP_NUM,

56. };

57. 
    

58. struct Cell{

59. Type _type;

60. int num;

61. };

62. 
    

63. Cell RPNExp[] = {

64. OP_NUM, 12,

65. OP_NUM, 3,

66. OP_NUM, 4,

67. ADD, 1,

68. MUL, 1,

69. OP_NUM, 6,

70. SUB, 1,

71. OP_NUM, 8,

72. OP_NUM, 2,

73. DIV, 1,

74. ADD, 1,

75. };

76. 
    

77. int main(){   

78. Stack<int> s2;    

79. int i = 0;

80. for (int i = 0; i < sizeof(RPNExp) / sizeof(RPNExp[0]);i++){  //取出元素

81.     int left, right;             //两个操作数

82. switch (RPNExp[i]._type){        //将栈中数据出栈

83. case ADD:                         //如果是加号，取两个操作数

84. left = s2.top();

85. s2.Pop();

86. right = s2.top();

87. s2.Pop();

88. s2.Push(left + right);         //新的值入栈

89. break;

90. case SUB:                       //如果是减号，取两个操作数

91. left = s2.top();

92. s2.Pop();

93. right = s2.top();

94. s2.Pop();

95. s2.Push(right - left);

96. break;

97. case MUL:                         //如果是乘号，取两个操作数

98. left = s2.top();

99. s2.Pop();

100. right = s2.top();

101. s2.Pop();

102. s2.Push(left * right);

103. break;

104. case DIV:                        //如果是除号，取两个操作数

105. left = s2.top();

106. s2.Pop();

107. right = s2.top();

108. s2.Pop();

109. s2.Push(right / left);

110. break;

111. case OP_NUM:                     //如果数字，入栈

112. s2.Push(RPNExp[i].num);

113. break;

114. default:

115. return -1;

116. }

117. }

118. cout << s2.top() << endl;

119. return 0;

120. }

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c++：栈的应用之表达式求值

原文：http://molova.blog.51cto.com/10594266/1705349