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Solution.java
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Solution.java
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package g0201_0300.s0227_basic_calculator_ii;
// #Medium #String #Math #Stack #Level_2_Day_18_Stack
// #2022_07_04_Time_8_ms_(95.32%)_Space_43.6_MB_(79.36%)
public class Solution {
public int calculate(String s) {
int sum = 0;
int tempSum = 0;
int num = 0;
char lastSign = '+';
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
if (Character.isDigit(c)) {
num = num * 10 + c - '0';
}
// i == s.length() - 1 will make sure that after last num is
// made and there is nothing to read anything from 's', the final computation is done
if (i == s.length() - 1 || !Character.isDigit(c) && c != ' ') {
switch (lastSign) {
case '+':
sum += tempSum;
tempSum = num;
break;
case '-':
sum += tempSum;
tempSum = -num;
break;
case '*':
tempSum *= num;
break;
case '/':
if (num != 0) {
tempSum /= num;
}
break;
default:
break;
}
lastSign = c;
num = 0;
}
}
// finally, add tempSum to sum
sum += tempSum;
return sum;
}
}