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  1. #include <stdio.h>
  2. #include <ctype.h>
  3.  
  4. char postfix[64] = {0};
  5. char stack[64] = {0};
  6. int top_p = 0;
  7. int top_s = 0;
  8.  
  9. void
  10. push_s(char d)
  11. {
  12.     stack[top_s] = d;
  13.     top_s++;
  14. }
  15.  
  16. void
  17. push_p(char d)
  18. {
  19.     postfix[top_p] = d;
  20.     top_p++;
  21. }
  22.  
  23. int
  24. _pop_s(void)
  25. {
  26.     top_s--;
  27.     return stack[top_s];
  28. }
  29.  
  30. void
  31. stack_init(void)
  32. {
  33.     stack[top_s] = 0x00;
  34. }
  35.  
  36. int
  37. pop_s(void)
  38. {
  39.     char d;
  40.     d = _pop_s();
  41.     stack_init();
  42.     return d;
  43. }
  44.  
  45. int
  46. _pop_p()
  47. {
  48.     top_p--;
  49.     return postfix[top_p];
  50. }
  51.  
  52. void
  53. postfix_init(void)
  54. {
  55.     postfix[top_p] = 0x00;
  56. }
  57.  
  58. int
  59. pop_p(void)
  60. {
  61.     char d;
  62.     d = _pop_p();
  63.     postfix_init();
  64.     return d;
  65. }
  66.  
  67. void
  68. infix_to_postfix(char *in)
  69. {
  70.     char operator[256] = {0};
  71.  
  72.     operator['('] = 0;
  73.     operator['+'] = 1;
  74.     operator['-'] = 1;
  75.     operator['*'] = 2;
  76.     operator['/'] = 2;
  77.     while (*in) {
  78.         if (isdigit(*in)) {
  79.             push_p(*in);
  80.         } else { /* operator */
  81.             while (1) {
  82.                 switch (*in) {
  83.                 case '(':
  84.                     push_s(*in);
  85.                     break;
  86.                 case ')':
  87.                     while (stack[top_s -1] != '(') {
  88.                         push_p(pop_s());
  89.                     }
  90.                     pop_s();
  91.                     break;
  92.                 default:
  93.                     break;
  94.                 }
  95.                 if (*in == '(' || *in == ')') {
  96.                     break;
  97.                 }
  98.                 if (!stack[top_s]) {
  99.                     while (operator[stack[top_s - 1]] >= operator[*in]) {
  100.                         push_p(pop_s());
  101.                         if (stack[top_s - 1]) {
  102.                             break;
  103.                         }
  104.                     }
  105.                 }
  106.                 break;
  107.             }
  108.             if (*in != '(' || *in != ')') {
  109.                 push_s(*in);
  110.             }
  111.         }
  112.         in++;
  113.     }
  114. }
  115.  
  116. void
  117. stack_empty()
  118. {
  119.     while (stack[top_s - 1]) {
  120.         push_p(pop_s());
  121.     }
  122. }
  123.  
  124. int
  125. main(int argc, char **argv)
  126. {
  127.     char infix[] = "1+2-3*4/3";
  128.  
  129.     infix_to_postfix(infix);
  130.     stack_empty();
  131.     printf("%s\n", postfix);
  132.     return 0;
  133. }
  134.  
Success #stdin #stdout 0s 2292KB
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Standard input is empty
stdout
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12+34*3/-
https://ideone.com/yek5LE
language:
C (gcc 8.3)
created:
10 years ago
visibility:
public

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