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  1. #include <stdio.h>
  2. #include <ctype.h>
  3.  
  4. char const *
  5. calculate( char const * input, 
  6.                int * value )
  7. {
  8.         char ch = *input;
  9.  
  10.         if( isdigit(ch) ) {
  11.                 *value = ch - '0';
  12.                 return input + 1;
  13.         }
  14.  
  15.         int left, right;
  16.         input = calculate( input+1, &left );
  17.         input = calculate( input, &right );
  18.  
  19.         switch( ch ) {
  20.         case '+':
  21.                 *value = left + right;
  22.                 break;
  23.         case '-':
  24.                 *value = left - right;
  25.                 break;
  26.         case '*':
  27.                 *value = left * right;
  28.                 break;
  29.         case '/':
  30.                 *value = left / right;
  31.                 break;
  32.         default:
  33.                 // should not reach here
  34.                 break;
  35.         }
  36.  
  37.         return input;
  38. }
  39.  
  40.  
  41. int main() {
  42.  
  43.         char const * input = "+1+*23*45";
  44.         int result;
  45.  
  46.         calculate( input, &result );
  47.  
  48.         printf( "result is : %d\n", result );
  49.  
  50.         return 0;
  51. }
Success #stdin #stdout 0.01s 1676KB
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stdin
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Standard input is empty
stdout
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result is : 27
https://ideone.com/Raflr
language:
C (gcc 8.3)
created:
13 years ago
visibility:
public

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