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  1.  #include <stdio.h>
  2. #include <string.h>
  3. #include <ctype.h>
  4. #include <stdlib.h>
  5.  
  6. struct node {
  7. int data;
  8. struct node *next;
  9. };
  10.  struct node *top = NULL;
  11.  
  12.  
  13. void push(int data);
  14. int pop();
  15. int evaluatePostfix(char* exp);
  16.  
  17. void main() {
  18.      char postfixExp[256];
  19.  
  20.      printf("What is your Postfix Expression? : \n");
  21.  
  22.      fgets(postfixExp, sizeof(postfixExp), stdin);
  23.      // printf("size of exp is %ld",strlen(postfixExp));
  24.      printf("%d\n", evaluatePostfix(postfixExp));
  25. }
  26.  
  27. //done
  28. void push(int data) {
  29. 	// data=atoi(data);
  30.      struct node *newNode;
  31.      newNode = (struct node*)malloc(sizeof(struct node));;
  32.      (*newNode).data = data;
  33.      (*newNode).next = NULL;
  34.      //use isEmpty if can
  35.      if (top != NULL) {
  36.          (*newNode).next = top;
  37.      }
  38.      top = newNode;
  39. }
  40. //done
  41. int pop() {
  42.     struct node *temp = top;
  43.     int removed;
  44.     //use isEmpty if can
  45.     if (top != NULL) {
  46.         removed = (*top).data;
  47.         top = (*top).next;
  48.         free(temp);
  49.     }
  50. return removed;
  51.  
  52. }
  53.  
  54.  int evaluatePostfix(char* exp) {
  55.      struct node *top = NULL;
  56.      printf("sizeof exp is %ld",strlen(exp));
  57.      for (int i = 0; i < strlen(exp)-1; i++) {
  58.       if (isdigit(exp[i])) {
  59.         push(exp[i]-48);
  60.     } else {
  61.         int val1 = pop();
  62.         int val2 = pop();
  63. 	printf("val1%d\n",val1);
  64. 	printf("val2%d\n",val2);
  65.         switch(exp[i]) {
  66.             case '+':
  67.                 push(val2+val1);
  68.                 break;
  69.             case '-':
  70.                 push(val2-val1);
  71.                 break;
  72.             case '*':
  73.                 push(val2*val1);
  74.                 break;
  75.             case '/':
  76.                 push(val2/val1);
  77.                 break;
  78.         }
  79.     }
  80. }
  81. return pop();
  82.  
  83. }
  84.  
Runtime error #stdin #stdout 0s 2296KB
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stdin
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Standard input is empty
stdout
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Standard output is empty
https://ideone.com/z58Phy
language:
C (gcc 8.3)
created:
8 years ago
visibility:
public

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