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BasicCalculatorII.java
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BasicCalculatorII.java
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package Leetcode;
/**
* Given a string s which represents an expression, evaluate this expression and return its value.
*
* The integer division should truncate toward zero.
*
* Example 1:
*
* Input: s = "3+2*2"
* Output: 7
* Example 2:
*
* Input: s = " 3/2 "
* Output: 1
* Example 3:
*
* Input: s = " 3+5 / 2 "
* Output: 5
*
*
* Constraints:
*
* 1 <= s.length <= 3 * 105
* s consists of integers and operators ('+', '-', '*', '/') separated by some number of spaces.
* s represents a valid expression.
* All the integers in the expression are non-negative integers in the range [0, 231 - 1].
* The answer is guaranteed to fit in a 32-bit integer.
*/
public class BasicCalculatorII {
public static int calculate(String s) {
int result = 0;
int number = 0;
int tempSum = 0;
char operator = '+';
for(int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
if(Character.isDigit(c))
number = number * 10 + (int)(c - '0');
if(i == s.length() -1 || (!Character.isDigit(c) && c != ' ')) {
switch(operator) {
case '+':
result += tempSum;
tempSum = number;
break;
case '-':
result += tempSum;
tempSum = -number;
break;
case '*':
tempSum *= number;
break;
case '/':
tempSum /= number;
break;
}
operator = c;
number = 0;
}
}
result += tempSum;
return result;
}
public static void main(String[] args) {
String str = "3 + 5 /2";
System.out.println(calculate(str));
}
}