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WordMachine.cpp
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WordMachine.cpp
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// Last sanity check: 2020-05-18
// you can use includes, for example:
#include <algorithm>
#include <iostream>
#include <string>
#include <cstring>
#include <sstream>
#include <vector>
using namespace std;
/* Attention:
* - 20bit int!
* - Don't leave the stack empty after operations!
* - Verify operations and input
* - Verify negative results
* - return -1 if an error is encountered
* Approach: Verify input; Decode word instructions; Compute;
*
*/
int solution(string &S)
{
int no, intBuf, int1, int2, pos;
vector <int> numbers;
string pop = "POP";
string dup = "DUP";
string add = "+";
string sub = "-";
//Reading words one by one
istringstream x(S);
string a;
while (x >> a)
if (a == dup)
{
if(!numbers.empty())
{
intBuf = numbers.back();
numbers.push_back(intBuf);
}
}
else if (a == pop)
{
numbers.pop_back();
}
else if (a == add)
{
if (numbers.size() < 1) return -1;
else
{
pos = numbers.size() - 1;
int1 = numbers[pos];
int2 = numbers[pos-1];
numbers.pop_back();
if (numbers.size() < 1) return -1;
numbers.pop_back();
numbers.push_back(int1+int2);
}
}
else if (a == sub)
{
if (numbers.size() < 1) return -1;
else
{
pos = numbers.size() - 1;
int1 = numbers[pos];
int2 = numbers[pos-1];
numbers.pop_back();
if (numbers.size() < 1) return -1;
numbers.pop_back();
if ( (int1-int2) < 0 ) return -1;
else numbers.push_back(int1-int2);
}
}
else
{
no = stoi (a);
if (no < 0) return -1;
else
numbers.push_back(no);
}
return numbers.back();
}