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basic_calc.cpp
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basic_calc.cpp
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#include <iostream>
#include <stack>
using namespace std;
// a calculator for addition and subtraction only
int main ()
{
string s = " 2-1 + 2 ";
stack<char> st;
int size = s.length();
for (int i = 0; i < size; i++) {
if (s[i] == ')') {
int calculation = 0;
char left_op = 1;
stack<char> st2;
while (st.top() != '(') {
st2.push(st.top());
st.pop();
}
while (!st2.empty()) {
char c = st2.top();
st2.pop();
if (isdigit(c)) {
int num = c - '0';
while (!st2.empty() && isdigit(st2.top())) {
num = num * 10 + st2.top() - '0';
st2.pop();
}
calculation += left_op * num;
left_op = 1;
} else {
if (c == '-') {
left_op *= -1;
}
}
}
st.pop(); // pop '('
string a = to_string(calculation);
for (char ch : a) {
st.push(ch);
}
} else if (s[i] != ' ') {
st.push(s[i]);
}
}
int calculation = 0;
int left_op = 1;
stack<char> st2;
string ans;
while (!st.empty()) {
st2.push(st.top());
st.pop();
}
while (!st2.empty()) {
char c = st2.top();
st2.pop();
ans += c;
}
int size2 = ans.length();
for (int i = 0; i < size2; i++) {
if (isdigit(ans[i])) {
int num = ans[i] - '0'; // Convert character to integer
// If the next character is also a digit, build the complete number
while (i + 1 < size && isdigit(ans[i + 1])) {
num = num * 10 + (ans[i + 1] - '0');
i++;
}
calculation += left_op * num;
left_op = 1;
} else {
if (ans[i] == '-') {
left_op *= -1;
}
}
}
cout << calculation;
return 0;
}