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  1. #include <stdio.h>
  2. #include <string.h>
  3. #include <ctype.h>
  4.  
  5. char stack[100];
  6. char input[100];
  7. int top = -1;
  8.  
  9. void printStack()
  10. {
  11.     int i;
  12.     for(i = 0; i <= top; i++)
  13.         printf("%c", stack[i]);
  14.     printf("\n");
  15. }
  16.  
  17. void reduce()
  18. {
  19.     int changed = 1;
  20.  
  21.     while(changed)
  22.     {
  23.         changed = 0;
  24.  
  25.         if(top >= 0 &&
  26.            stack[top] >= 'a' &&
  27.            stack[top] <= 'z')
  28.         {
  29.             stack[top] = 'E';
  30.             printf("Reduce: ");
  31.             printStack();
  32.             changed = 1;
  33.         }
  34.  
  35.         if(top >= 2 &&
  36.            stack[top-2] == '(' &&
  37.            stack[top-1] == 'E' &&
  38.            stack[top] == ')')
  39.         {
  40.             top -= 2;
  41.             stack[top] = 'E';
  42.             printf("Reduce: ");
  43.             printStack();
  44.             changed = 1;
  45.             continue;
  46.         }
  47.  
  48.         if(top >= 2 &&
  49.            stack[top-2] == 'E' &&
  50.            stack[top-1] == '+' &&
  51.            stack[top] == 'E')
  52.         {
  53.             top -= 2;
  54.             stack[top] = 'E';
  55.             printf("Reduce: ");
  56.             printStack();
  57.             changed = 1;
  58.             continue;
  59.         }
  60.  
  61.         if(top >= 2 &&
  62.            stack[top-2] == 'E' &&
  63.            stack[top-1] == '*' &&
  64.            stack[top] == 'E')
  65.         {
  66.             top -= 2;
  67.             stack[top] = 'E';
  68.             printf("Reduce: ");
  69.             printStack();
  70.             changed = 1;
  71.             continue;
  72.         }
  73.     }
  74. }
  75.  
  76. int main()
  77. {
  78.     int ptr = 0;
  79.     int i, len;
  80.  
  81.     printf("Enter an Expression: ");
  82.     fgets(input, sizeof(input), stdin);
  83.  
  84.     char exp[100];
  85.     int j = 0;
  86.  
  87.     for(i = 0; input[i] != '\0'; i++)
  88.     {
  89.         if(input[i] != ' ' &&
  90.            input[i] != '\t' &&
  91.            input[i] != '\n')
  92.         {
  93.             exp[j++] = input[i];
  94.         }
  95.     }
  96.  
  97.     exp[j] = '\0';
  98.     len = strlen(exp);
  99.  
  100.     while(ptr < len)
  101.     {
  102.         stack[++top] = exp[ptr++];
  103.         printf("Shift: ");
  104.         printStack();
  105.  
  106.         reduce();
  107.     }
  108.  
  109.     reduce();
  110.  
  111.     if(top == 0 && stack[0] == 'E')
  112.         printf("String Accepted\n");
  113.     else
  114.         printf("String Rejected\n");
  115.  
  116.     return 0;
  117. }
Success #stdin #stdout 0s 5324KB
comments (?)
stdin
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(a + (b*a))
stdout
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Enter an Expression: Shift: (
Shift: (a
Reduce: (E
Shift: (E+
Shift: (E+(
Shift: (E+(b
Reduce: (E+(E
Shift: (E+(E*
Shift: (E+(E*a
Reduce: (E+(E*E
Reduce: (E+(E
Shift: (E+(E)
Reduce: (E+E
Reduce: (E
Shift: (E)
Reduce: E
String Accepted
https://ideone.com/RPa056
language:
C (gcc 8.3)
created:
8 hours ago
visibility:
public

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