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  1. #include <stdio.h>
  2. #include <string.h>
  3.  
  4. char stack[100][10];
  5. int top = -1;      
  6. int pos = 0;       
  7. char input[100];   
  8.  
  9.  
  10. void push(const char *s)
  11. {
  12.     strcpy(stack[++top], s);
  13. }
  14.  
  15. void pop()
  16. {
  17.     top--;
  18. }
  19.  
  20.  
  21. void printStack()
  22. {
  23.     for (int i = 0; i <= top; i++) {
  24.         printf("%s", stack[i]);
  25.         if (i < top) printf(" ");
  26.     }
  27.     printf("\n");
  28. }
  29.  
  30.  
  31. int reduce()
  32. {
  33.     // Rule 1: E → E + E
  34.     if (top >= 2 &&
  35.             strcmp(stack[top-2], "E")==0 &&
  36.             strcmp(stack[top-1], "+")==0 &&
  37.             strcmp(stack[top], "E")==0)
  38.     {
  39.         pop();
  40.         pop();
  41.         pop();   
  42.         push("E");          
  43.         return 1;              
  44.     }
  45.  
  46.  
  47.     if (top >= 2 &&
  48.             strcmp(stack[top-2], "E")==0 &&
  49.             strcmp(stack[top-1], "*")==0 &&
  50.             strcmp(stack[top], "E")==0)
  51.     {
  52.         pop();
  53.         pop();
  54.         pop();   
  55.         push("E");
  56.         return 1;
  57.     }
  58.  
  59.  
  60.     if (top >= 2 &&
  61.             strcmp(stack[top-2], "(")==0 &&
  62.             strcmp(stack[top-1], "E")==0 &&
  63.             strcmp(stack[top], ")")==0)
  64.     {
  65.         pop();
  66.         pop();
  67.         pop();   
  68.         push("E");
  69.         return 1;
  70.     }
  71.  
  72.  
  73.     if (top!=-1 && stack[top][0]>='a'&&stack[top][0]<='z')
  74.     {
  75.         pop();  
  76.         push("E");  
  77.         return 1;
  78.     }
  79.  
  80.     return 0; 
  81. }
  82.  
  83. int main()
  84. {
  85.  
  86.     printf("Enter an Expression:\n");
  87.  
  88.  
  89.     fgets(input, sizeof(input), stdin);
  90.  
  91.  
  92.     int len = strlen(input);
  93.     if (len > 0 && input[len-1] == '\n') {
  94.         input[len-1] = '\0';
  95.     }
  96.  
  97.  
  98.     pos = 0;
  99.     while (input[pos])
  100.     {
  101.  
  102.         while (input[pos] == ' ' || input[pos] == '\t') {
  103.             pos++;
  104.         }
  105.  
  106.         if (!input[pos]) break;  
  107.  
  108.  
  109.         char temp[2] = {input[pos], '\0'};
  110.         push(temp);
  111.         pos++;        
  112.  
  113.  
  114.         printf("Shift: ");
  115.         printStack();
  116.  
  117.         while (reduce())
  118.         {
  119.             printf("Reduce: ");
  120.             printStack();
  121.         }
  122.     }
  123.  
  124.  
  125.     if (top == 0 && strcmp(stack[0], "E")==0)
  126.         printf("String Accepted\n");
  127.     else
  128.         printf("String Rejected\n");
  129.  
  130.     return 0;
  131. }
Success #stdin #stdout 0s 5328KB
comments (?)
stdin
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a+b*( g)
stdout
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Enter an Expression:
Shift: a
Reduce: E
Shift: E +
Shift: E + b
Reduce: E + E
Reduce: E
Shift: E *
Shift: E * (
Shift: E * ( g
Reduce: E * ( E
Shift: E * ( E )
Reduce: E * E
Reduce: E
String Accepted
https://ideone.com/m3uTin
language:
C (gcc 8.3)
created:
16 hours ago
visibility:
public

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