UVA_327_Evaluating Simple C Expressions

#include<iostream>
#include<sstream>
#include<string>
#include<vector>
#include<list>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<algorithm>
#include<bitset>
#pragma warning(disable:4996)
using std::cin;
using std::cout;
using std::endl;
using std::stringstream;
using std::string;
using std::vector;
using std::list;
using std::pair;
using std::set;
using std::multiset;
using std::map;
using std::multimap;
using std::stack;
using std::queue;
using std::priority_queue;
using std::bitset;
void evaluate(const string &str)
{
map<char, int>char_val;
char Operator = '+';
int sum = 0;
for (size_t i = 0; i < str.size();)
{
if (str.size() - i >= 3)
{
if (str[i] == '+'&&str[i + 1] == '+'&&isalpha(str[i + 2]))
{
if (Operator == '+')
{
sum += str[i+2] - 'a' + 2;
}
else
{
sum -= str[i+2] - 'a' + 2;
}
char_val.insert({ str[i+2],str[i+2]-'a' + 2 });
}
else if (str[i] == '-'&&str[i + 1] == '-'&&isalpha(str[i + 2]))
{
if (Operator == '+')
{
sum += str[i+2] - 'a';
}
else
{
sum -= str[i+2] - 'a';
}
char_val.insert({ str[i+2],str[i+2] - 'a' });
}
else if (isalpha(str[i]) && str[i + 1] == '+'&&str[i + 2] == '+')
{
if (Operator == '+')
{
sum += str[i] - 'a' + 1;
}
else
{
sum -= str[i] - 'a' + 1;
}
char_val.insert({ str[i],str[i] - 'a' + 2 });
}
else if (isalpha(str[i]) && str[i + 1] == '-'&&str[i + 2] == '-')
{
if (Operator == '+')
{
sum += str[i] - 'a' + 1;
}
else
{
sum -= str[i] - 'a' + 1;
}
char_val.insert({ str[i],str[i] - 'a' });
}
else
{
goto sign;
}
i += 3;
}
else
{
sign:
if (isalpha(str[i]))
{
if (Operator == '+')
{
sum += str[i] - 'a' + 1;
}
else
{
sum -= str[i] - 'a' + 1;
}
char_val.insert({str[i],str[i]-'a'+1});
}
else
{
Operator = str[i];
}
i++;
}
}
cout << "    value = " << sum << endl;
for (auto iter = char_val.begin(); iter != char_val.end(); iter++)
{
cout << "    " << iter->first << " = " << iter->second << endl;
}
}
string clear_space(const string &str)
{
string ret;
for (size_t i = 0; i < str.size(); i++)
{
if (!isspace(str[i]))
{
ret.push_back(str[i]);
}
}
return ret;
}
int main()
{
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
string expression;
while (getline(cin, expression))
{
cout << "Expression: " << expression << endl;
expression = clear_space(expression);
evaluate(expression);
}
return 0;
}