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  1. #include <iostream>
  2. #include <stdlib.h>
  3. #include <stack>
  4. #include <string.h>
  5. #include <sys/stat.h>
  6. #include <sys/types.h>
  7. #include <unistd.h>
  8. //#include <strstream.h>
  9.  
  10.  
  11. using namespace std;
  12.  
  13. bool isOperator(char ch)
  14. {
  15.     if (ch=='+' || ch=='-' || ch=='*' || ch=='/')
  16.         return true;
  17.     else
  18.         return false;
  19. }
  20.  
  21.  
  22. int performOperation(int op1, int op2, char op)
  23. {
  24.     int ans;
  25.     switch(op){
  26.     case '+':
  27.         ans = op2 + op1;
  28.         break;
  29.     case '-':
  30.         ans = op2 - op1;
  31.         break;
  32.     case '*':
  33.         ans = op2 * op1;
  34.         break;
  35.     case '/':
  36.         ans = op2 / op1;
  37.         break;
  38.     }
  39.     return ans;
  40. }
  41.  
  42.  
  43. int main()
  44. {
  45.     char exp[1000]="", buffer[15]="";
  46.     int i=0,op1=0, op2=0, len=0, j=0, x=0, elemntCnt=0;
  47.     stack<int> s;
  48.     gets(exp);
  49.     cout <<"Enter a Postfix Expression: ( e.g. 23 34 * )" << endl;
  50.  
  51.     len = strlen(exp);
  52.     cout << "length of expression:"<<len<<endl;
  53.     j = 0;
  54.  
  55.     if (len > 0)
  56.     {
  57. 	    for(i=0; i<len;i++)
  58. 	    {
  59. 		if(exp[i]>='0' && exp[i]<='9')
  60. 		{
  61. 		    buffer[j++] = exp[i];
  62. 		}
  63. 		else if(exp[i]==' ')
  64. 		{
  65. 		    if(j>0)
  66. 		    {
  67. 			buffer[j] = '\0';
  68. 			x = atoi(buffer);
  69. 			s.push(x);
  70. 			memset(buffer, '\0', sizeof(buffer));
  71. 			j = 0;
  72. 			elemntCnt++;
  73. 		    }
  74. 		}
  75. 		else if(isOperator(exp[i]))
  76. 		{
  77. 		    if (elemntCnt<2)
  78. 		    {
  79. 		       cout <<"invalid format" << endl;
  80. 		       break;
  81. 		    }
  82. 		    else
  83. 		    {
  84. 			    op1 = s.top();
  85. 			    s.pop();
  86. 			    op2 = s.top();
  87. 			    s.pop();
  88. 			    cout << "Performing operation "<<op1<<exp[i]<<op2<<endl;
  89. 			    s.push(performOperation(op1, op2, exp[i]));
  90. 		    	    cout <<"Answer for above is ::" << s.top() << endl;
  91.  
  92. 		    }
  93. 		}
  94. 		else
  95. 		{
  96. 		    cout <<"invalid characters in expression" << endl;
  97. 		    break;
  98. 		}
  99. 	    }//end for
  100.     }
  101.     else
  102.     {
  103.           cout <<"Exiting" << endl;
  104.     }
  105.     return 0;
  106. }
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin
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Standard input is empty
compilation info 
prog.cpp:48:5: error: use of undeclared identifier 'gets'
    gets(exp);
    ^
1 error generated.
stdout
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Standard output is empty
https://ideone.com/rfhpyi
language:
C++14 (clang 8.0)
created:
8 years ago
visibility:
public

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