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| class Solution {
public:
int calculate(string s) {
char preSign = '+';
long num = 0;
int sz = s.size();
vector<int> st;
for(int i = 0; i < sz; ++i)
{
auto ch = s[i];
if(isdigit(ch))
num = num * 10 + ch - '0';
if((!isdigit(ch) && ch != ' ') || i == sz - 1)
{
switch(preSign)
{
case '+':
st.push_back(num);
break;
case '-':
st.push_back(-num);
break;
case '*':
st.back() *= num;
break;
case '/':
st.back() /= num;
}
num = 0;
preSign = ch;
}
}
return accumulate(st.begin(), st.end(), 0);
}
};
|