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