Solve arithematic expressions.txt

#include <stdio.h>
#include<string.h>

int addsub();
int muldiv();
int term();

char input[101];
int pos = 0;

int term(){
  int n = 0;

  if(input[pos] == '('){
    pos++;
    n = addsub();
    
    if(input[pos] == ')'){
      pos++;
      return n;
    }
  }else{
    while('0' <= input[pos] && input[pos] <= '9'){
      n = n*10 + (input[pos] - '0');
      pos++;
    }
  }
  return n;
}

int muldiv(){
  int first,second;
  
  first = term();
  for(;;){
    if(input[pos] == '*'){
      pos++;
      second = term();
      first *= second; 
    }else if(input[pos] == '/'){
      pos++;
      second = term();
      first /= second;
    }else{
      return first;
    }
  }
}

int addsub(){
  int first,second;
  
  first = muldiv();
  
  for(;;){
    if(input[pos] == '+'){
      pos++;
      second = muldiv();
      first += second; 
    }else if(input[pos] == '-'){
      pos++;
      second = muldiv();
      first -= second;
    }else{
      return first;
    }
  }
  
}

int main(){
  int n,i,j;
  printf("Input an expression using +, -, *, / operators:\n");
  scanf("%s",input);
  printf("%d\n",addsub());  
  return 0;
  }