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Cod sursa(job #735636)
#include <stack>
#include <string>
#include <fstream>
#include <cstdlib>
using namespace std;
stack<int> dSt;
stack<char> cSt;
string exp, transf;
string::const_iterator it, iend;
inline int priority(char c)
{
switch(c)
{
case '(' : return 0;
case '+' : ;
case '-' : return 1;
case '*' : ;
case '/' : return 2;
case ')' : return 3;
default : return 5;
}
}
int main()
{
int pIt, x, a, b;
ifstream in("evaluare.in");
ofstream out("evaluare.out");
getline(in, exp);
for( it=exp.begin(), iend=exp.end(); it < iend; )
{
if(*it >= '0' && *it <= '9')
{
for( ; it < iend && *it >= '0' && *it <= '9'; ++it)
transf.push_back(*it);
transf.push_back(',');
}
else if('(' == *it)
{
cSt.push(*it);
++it;
}
else if(')' == *it)
{
for(++it; '(' != cSt.top(); transf.push_back(cSt.top()), cSt.pop());
cSt.pop();
}
else {
for(pIt=priority(*it); !cSt.empty() && pIt <= priority(cSt.top()); transf.push_back(cSt.top()), cSt.pop());
cSt.push(*it); ++it;
}
}
for(; !cSt.empty(); transf.push_back(cSt.top()), cSt.pop());
for(it=transf.begin(), iend=transf.end(); it < iend; ++it)
{
if(*it >= '0' && *it <= '9')
{
for(x=0; it < iend && *it >= '0' && *it <= '9'; ++it)
x=x*10+*it-'0';
dSt.push(x);
}
else {
x=priority(*it);
if(x >= 1 && x < 3)
{
b=dSt.top(); dSt.pop();
a=dSt.top(); dSt.pop();
switch(*it)
{
case '+' : dSt.push(a+b); break;
case '-' : dSt.push(a-b); break;
case '*' : dSt.push(a*b); break;
case '/' : dSt.push(a/b); break;
}
}
}
}
out<<dSt.top()<<'\n';
return EXIT_SUCCESS;
}