プログラマ専用SNS ミクプラ

コード:

#include<stdio.h>


char buf[10000];
int i;
char c;

int express();
int term();
int factor();

void next(){
  while(buf[i]==' ') 
	  i++;
  c = buf[1++];
}

int express(){
  int x = term();
  while(c == '+' || c== '-'){
    if(c == '+'){
      next();
      x = x + term();
    } else if(c == '-'){ 
      next();
      x = x - term();
    }
  }
  return x;
}

int term(){
  int y = factor();
  while(c== '*' || c== '/'){
    if(c=='*'){
      next();
      y =  y * factor();
    }else if(c=='/'){
      next();
      y = y / factor();
    }
  }  
  return y;
}

int factor(){
  int z = 0;
  if(c == '('){
    next();
    z = express();
  }else if(c >= '0' || c <= '9') 
	z = c - '0';
	next();
  return z;
}

int main(){
  fgets(buf,127,stdin);
  i = 0;
  next();
  printf("%d\n",express());
  return 0;
}