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| class Solution {
public int calculate(String s) {
char[] cs = s.toCharArray();
int n = cs.length, num = 0;
Deque<Integer> stack = new ArrayDeque<>();
char sign = '+';
for (int i = 0; i < n; ++i) {
char c = cs[i];
if (c >= '0' && c <= '9') {
num = num * 10 + (c - '0');
}
if (!(c >= '0' && c <= '9') && c != ' ' || i == n - 1) {
switch (sign) {
case '+' -> stack.push(num);
case '-' -> stack.push(-num);
case '*' -> stack.push(stack.pop() * num);
case '/' -> stack.push(stack.pop() / num);
}
sign = c;
num = 0;
}
}
int ans = 0;
while (!stack.isEmpty()) {
ans += stack.pop();
}
return ans;
}
}
|
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