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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4.  
  5. #define MAX_SIZE 100
  6.  
  7. // Define a stack structure
  8. struct Stack {
  9.     int top;
  10.     char items[MAX_SIZE];
  11. };
  12.  
  13. // Function to initialize an empty stack
  14. void initialize(struct Stack *s) {
  15.     s->top = -1;
  16. }
  17.  
  18. // Function to check if the stack is empty
  19. int isEmpty(struct Stack *s) {
  20.     return s->top == -1;
  21. }
  22.  
  23. // Function to push an element onto the stack
  24. void push(struct Stack *s, char item) {
  25.     if (s->top == MAX_SIZE - 1) {
  26.         printf("Stack Overflow\n");
  27.         exit(1);
  28.     }
  29.     s->items[++(s->top)] = item;
  30. }
  31.  
  32. // Function to pop an element from the stack
  33. char pop(struct Stack *s) {
  34.     if (isEmpty(s)) {
  35.         printf("Stack Underflow\n");
  36.         exit(1);
  37.     }
  38.     return s->items[(s->top)--];
  39. }
  40.  
  41. // Function to check precedence of operators
  42. int precedence(char operator) {
  43.     if (operator == '+' || operator == '-') {
  44.         return 1;
  45.     } else if (operator == '*' || operator == '/') {
  46.         return 2;
  47.     }
  48.     return 0;
  49. }
  50.  
  51. // Function to convert infix expression to postfix notation
  52. void infixToPostfix(char infix[], char postfix[]) {
  53.     struct Stack stack;
  54.     initialize(&stack);
  55.  
  56.     int i, j;
  57.     i = j = 0;
  58.  
  59.     while (infix[i] != '\0') {
  60.         char token = infix[i];
  61.  
  62.         if (token >= 'a' && token <= 'z') {
  63.             postfix[j++] = token;
  64.         } else if (token == '(') {
  65.             push(&stack, token);
  66.         } else if (token == ')') {
  67.             while (!isEmpty(&stack) && stack.items[stack.top] != '(') {
  68.                 postfix[j++] = pop(&stack);
  69.             }
  70.             if (!isEmpty(&stack) && stack.items[stack.top] == '(') {
  71.                 pop(&stack); // Pop the '('
  72.             }
  73.         } else {
  74.             while (!isEmpty(&stack) && precedence(token) <= precedence(stack.items[stack.top])) {
  75.                 postfix[j++] = pop(&stack);
  76.             }
  77.             push(&stack, token);
  78.         }
  79.  
  80.         i++;
  81.     }
  82.  
  83.     while (!isEmpty(&stack)) {
  84.         postfix[j++] = pop(&stack);
  85.     }
  86.  
  87.     postfix[j] = '\0';
  88. }
  89.  
  90. int main() {
  91.     char infix[MAX_SIZE] = "x+y"; // Predefined infix expression
  92.     char postfix[MAX_SIZE];
  93.  
  94.     infixToPostfix(infix, postfix);
  95.  
  96.     printf("Infix: %s\n", infix);
  97.     printf("Postfix: %s\n", postfix);
  98.  
  99.     return 0;
  100. }
  101.  
Success #stdin #stdout 0s 5476KB
comments (?)
stdin
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Standard input is empty
stdout
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Infix: x+y
Postfix: xy+
https://ideone.com/KCNDDm
language:
C (gcc 8.3)
created:
2 years ago
visibility:
public

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