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Basic Calculator II.java
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41 lines (40 loc) · 1.03 KB
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class Solution {
public int calculate(String s) {
char sign = '+';
int currNum = 0;
Stack<Integer> stack = new Stack<>();
for (int i = 0; i < s.length(); i++) {
if (Character.isDigit(s.charAt(i))) {
currNum = currNum * 10 + Character.getNumericValue(s.charAt(i));
}
if ((!Character.isDigit(s.charAt(i)) && s.charAt(i) != ' ') || i == s.length() - 1) {
updateStackForPreviousSign(sign, stack, currNum);
currNum = 0;
sign = s.charAt(i);
}
}
int result = 0;
while (!stack.isEmpty()) {
result += stack.pop();
}
return result;
}
private void updateStackForPreviousSign(char sign, Stack<Integer> stack, int currNum) {
switch (sign) {
case '+':
stack.push(currNum);
break;
case '-':
stack.push(-1 * currNum);
break;
case '/':
stack.push(stack.pop() / currNum);
break;
case '*':
stack.push(stack.pop() * currNum);
break;
default:
break;
}
}
}