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  1. #include <stdio.h>
  2. #include <string.h>
  3. #include <ctype.h>
  4.  
  5. char stack[100][10];
  6. int top = -1;
  7. int pos = 0;
  8. char input[100];
  9.  
  10. void push(const char *s) {
  11.     strcpy(stack[++top], s);
  12. }
  13.  
  14. void pop() {
  15.     top--;
  16. }
  17.  
  18. void printStack() {
  19.     for (int i = 0; i <= top; i++)
  20.         printf("%s", stack[i]);
  21.     printf("\n");
  22. }
  23.  
  24. // Reduce with lookahead
  25. int reduce(char lookahead) {
  26.  
  27.     // F -> id
  28.     if (top >= 0 &&
  29.         stack[top][0] >= 'a' &&
  30.         stack[top][0] <= 'z')
  31.     {
  32.         pop();
  33.         push("F");
  34.         return 1;
  35.     }
  36.  
  37.     // F -> (E)
  38.     if (top >= 2 &&
  39.         strcmp(stack[top-2], "(") == 0 &&
  40.         strcmp(stack[top-1], "E") == 0 &&
  41.         strcmp(stack[top], ")") == 0)
  42.     {
  43.         pop(); pop(); pop();
  44.         push("F");
  45.         return 1;
  46.     }
  47.  
  48.     // T -> T * F
  49.     if (top >= 2 &&
  50.         strcmp(stack[top-2], "T") == 0 &&
  51.         strcmp(stack[top-1], "*") == 0 &&
  52.         strcmp(stack[top], "F") == 0)
  53.     {
  54.         pop(); pop(); pop();
  55.         push("T");
  56.         return 1;
  57.     }
  58.  
  59.     // T -> F
  60.     if (top >= 0 && strcmp(stack[top], "F") == 0)
  61.     {
  62.         pop();
  63.         push("T");
  64.         return 1;
  65.     }
  66.  
  67.     // E -> E + T  (مع مراعاة precedence)
  68.     if (top >= 2 &&
  69.         strcmp(stack[top-2], "E") == 0 &&
  70.         strcmp(stack[top-1], "+") == 0 &&
  71.         strcmp(stack[top], "T") == 0)
  72.     {
  73.         // لو الجاي * نستنى
  74.         if (lookahead == '*')
  75.             return 0;
  76.  
  77.         pop(); pop(); pop();
  78.         push("E");
  79.         return 1;
  80.     }
  81.  
  82.     // ✅ التعديل هنا
  83.     // E -> T (مع مراعاة precedence)
  84.     if (top >= 0 && strcmp(stack[top], "T") == 0)
  85.     {
  86.         // لو الجاي * يبقى لسه هنكوّن T * F
  87.         if (lookahead == '*')
  88.             return 0;
  89.  
  90.         pop();
  91.         push("E");
  92.         return 1;
  93.     }
  94.  
  95.     return 0;
  96. }
  97.  
  98. int main() {
  99.     printf("Enter an Expression:\n");
  100.     fgets(input, 100, stdin);
  101.  
  102.     while (input[pos]) {
  103.  
  104.         if (isspace(input[pos])) {
  105.             pos++;
  106.             continue;
  107.         }
  108.  
  109.         char temp[2] = {input[pos], '\0'};
  110.         push(temp);
  111.         pos++;
  112.  
  113.         printf("Shift: ");
  114.         printStack();
  115.  
  116.         while (reduce(input[pos])) {
  117.             printf("Reduce: ");
  118.             printStack();
  119.         }
  120.     }
  121.  
  122.     while (reduce('\0')) {
  123.         printf("Reduce: ");
  124.         printStack();
  125.     }
  126.  
  127.     if (top == 0 && strcmp(stack[0], "E") == 0)
  128.         printf("String Accepted\n");
  129.     else
  130.         printf("String Rejected\n");
  131.  
  132.     return 0;
  133. }
Success #stdin #stdout 0.01s 5320KB
comments (?)
stdin
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(a+(b*a))
stdout
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Enter an Expression:
Shift: (
Shift: (a
Reduce: (F
Reduce: (T
Reduce: (E
Shift: (E+
Shift: (E+(
Shift: (E+(b
Reduce: (E+(F
Reduce: (E+(T
Reduce: (E+(E
Shift: (E+(E*
Shift: (E+(E*a
Reduce: (E+(E*F
Reduce: (E+(E*T
Reduce: (E+(E*E
Shift: (E+(E*E)
Shift: (E+(E*E))
String Rejected
https://ideone.com/WxOQSa
language:
C (gcc 8.3)
created:
1 day ago
visibility:
public

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