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| #include <stdio.h> | |
| #include <stdlib.h> | |
| #include <stdbool.h> | |
| #include <ctype.h> | |
| bool isValue( const char *exp ) | |
| { | |
| while(isdigit(*exp++) ); | |
| return !*(exp-1); | |
| } | |
| char *findNextOperator( char *exp ) | |
| { | |
| char *aux = NULL; | |
| while( *exp ) | |
| { | |
| if( *exp == '+' || *exp == '-' ) | |
| { | |
| return exp; | |
| } | |
| else if( !aux && (*exp == '*' || *exp == '/') ) | |
| { | |
| aux = exp; | |
| } | |
| exp++; | |
| } | |
| return aux; | |
| } | |
| int *eval( char *begin, char *end ) | |
| { | |
| char temp = *end; | |
| *end = '\0'; | |
| int *result = NULL; | |
| int *parcial1,*parcial2; | |
| char *operator; | |
| if( isValue(begin) ) | |
| { | |
| result = malloc(sizeof(int) ); | |
| *result = atoi(begin); | |
| } | |
| else | |
| { | |
| operator = findNextOperator( begin ); | |
| if( operator ) | |
| { | |
| result = malloc(sizeof(int) ); | |
| parcial1 = eval( begin, operator); | |
| parcial2 = eval( operator + 1, end); | |
| switch(*operator ) | |
| { | |
| case '*': *result = *parcial1 * *parcial2; break; | |
| case '/': *result = *parcial1 / *parcial2; break;/*tratar divião por 0*/ | |
| case '+': *result = *parcial1 + *parcial2; break; | |
| case '-': *result = *parcial1 - *parcial2; break; | |
| } | |
| free( parcial1); | |
| free( parcial2); | |
| } | |
| } | |
| *end = temp; | |
| return result; | |
| } | |
| int main(int argc, char const *argv[]) | |
| { | |
| char exp[ ] = "40-3*6"; | |
| int *ret = eval( exp, exp + sizeof exp ); | |
| if( ret ) | |
| { | |
| printf("%d",*ret); | |
| } | |
| return 0; | |
| } |
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