sisoku.cpp

#include <cstdio>
#include <cstring>
using namespace std;

double expr(char*);
double term(char*);
double elem(char*);

double expr(char *a)
{
  int id = 0, cnt = 0, s = 1;
	double ret = 0;
	while(1)
	{
		if(a[id] == '(')
			cnt++;

		if(a[id] == ')')
			cnt--;

		if( (a[id] == '+' || a[id] == '-' || a[id] == '\0') && cnt == 0)
		{
			char b[100];
			strncpy(b, a, id);
			b[id] = '\0';
			ret += term(b) * s;
			if(a[id] == '+')
				s = 1;
			else if(a[id] == '-')
				s = -1;
			else
				break;

			a += id + 1;
			id = 0;
		}
		id++;
	}
	return ret;

}

double term(char *a)
{
	int id = 0, cnt = 0;
	double ret = 0;
	bool s = true, f = true;

	while(1)
	{
		if(a[id] == '(')
			cnt++;

		if(a[id] == ')')
			cnt--;

		if( (a[id] == '*' || a[id] == '/' || a[id] == '\0') && cnt == 0)
		{
			char b[100];
			strncpy(b, a, id);
			b[id] = '\0';
			double e = elem(b);

			if(f)
			{
				ret = e;
				f = false;
			}
			else
			{
				if(s)
					ret *= e;
				else
					ret /= e;
			}

			if(a[id] == '*')
				s = true;
			else if(a[id] == '/')
				s = false;
			else
				break;

			a += id + 1;
			id = 0;
		}

		id++;
	}
	return ret;

}

double elem(char *a)
{
	double ret = 0;
	if(a[0] == '(')
	{
		a++;
		a[strlen(a) - 1] = '\0';
		ret = expr(a);
	}
	else
	{
		double e;
		sscanf(a, "%lf", &e);
		ret = e;
	}
	return ret;
}

int main()
{
	char a[501];
	fgets(a, 500, stdin);
	a[strlen(a) - 1] = '\0';
	printf("%.2lf\n", expr(a));
	return 0;
}