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  1. #include<stdio.h>
  2. #include<stdlib.h>
  3. #include<string.h>
  4. #define SIZE 50
  5. int top=-1;
  6. int top_post = -1;
  7. void push(char symbol);
  8. char pop();
  9. char stack[SIZE],infix[SIZE],post[SIZE],a;
  10. int precedence(char symbol)
  11. {
  12.     switch (symbol)
  13.     {
  14.     case '+':
  15.     case '-':
  16.         return 1;
  17.  
  18.     case '*':
  19.     case '/':
  20.         return 2;
  21.  
  22.     case '^':
  23.         return 3;
  24.     default:
  25.         return -1;
  26.     }
  27. }
  28. int highest_precedence()
  29. {
  30.     int high = 0;
  31.     for (int i = top; i >= 0; i--)
  32.     {
  33.         char symbol = stack[i];
  34.         if (symbol == '(')
  35.             break;
  36.         int now = precedence(symbol);
  37.  
  38.         if (now != -1)
  39.         {
  40.  
  41.             if (now > high)
  42.             {
  43.                 high = now;
  44.             }
  45.         }
  46.     }
  47.     return high;
  48. }
  49.  
  50. void push(char symbol)
  51. {
  52.     if(top>=SIZE-1)
  53.     {
  54.         printf("overflow");
  55.         exit(1);
  56.     }
  57.     else
  58.     {
  59.         top++;
  60.         stack[top]=symbol;
  61.     }
  62. }
  63. char pop()
  64. {
  65.     if (top<0)
  66.         printf("underflow\n");
  67.     else 
  68.     {
  69.         top--;
  70.         return stack[top+1];
  71.     }
  72. }
  73. void append(char symbol)
  74. {
  75.     if(top>=SIZE-1)
  76.     {
  77.         printf("overflow\n");
  78.         exit(1);
  79.     }
  80.     else
  81.     {
  82.         top_post++;
  83.         post[top_post]=symbol;
  84.     }
  85. }
  86. int main()
  87. {
  88.     char del;
  89.     gets(infix);
  90.     int len=strlen(infix);
  91.  
  92.     for (int i=0;i<len;i++)
  93.         {
  94.             char symbol=infix[i];
  95.             switch (symbol)
  96.             {
  97.             case '+':
  98.             case '-':
  99.             case '*':
  100.             case '/':
  101.             case '^':
  102.                     if (top != -1 && highest_precedence()>=precedence(symbol))// checks if the current symbol being scanned has the highest precedence
  103.                     {
  104.                         append(pop());//  prints to postfix
  105.                     }
  106.                     push(symbol);// pushes to stack
  107.                 break;
  108.             case '(':
  109.                     push(symbol);
  110.                     break;
  111.             case ')':
  112.                     while((del = pop()) != '(') //pops all elements and prints them until '(' is encountered.
  113.                         append(del);
  114.                     break;
  115.             default:
  116.                 append(symbol);
  117.             }
  118.         }
  119.     while(top!=-1)
  120.         append(pop());
  121.     append('\0');
  122.     for(int i=0;i<top_post;i++)
  123.         {
  124.         printf("%c  ",post[i]);
  125.         }
  126.         printf("\n");
  127.         return 0;
  128. }
Success #stdin #stdout 0s 5400KB
comments (?)
stdin 
Standard input is empty
stdout 

	

		
	 
	
	
			

					
			
			
			
			
			
			
			
			

			
			
			
		

	
		
		

			


			                        
			
			

				

	
					
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language:

						
C (gcc 8.3)

					

					

						
created:
								
						
2 years ago

					

					

						
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