-
Notifications
You must be signed in to change notification settings - Fork 2
/
BasicCalculatorII.java
65 lines (57 loc) · 1.37 KB
/
BasicCalculatorII.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
package com.algorithm.playground.leetcode.problems.lc200.lc220.lc227;
import java.util.LinkedList;
/**
* https://leetcode.com/problems/basic-calculator-ii/
*/
public class BasicCalculatorII {
class Solution {
public int calculate(String s) {
LinkedList<Integer> ints = new LinkedList<>();
LinkedList<Character> ops = new LinkedList<>();
Character curr = null;
for (int i = 0; i < s.length(); i++) {
char ch = s.charAt(i);
if (Character.isDigit(ch)) {
Integer n = ch - '0';
while (i + 1 < s.length() && Character.isDigit(s.charAt(i + 1))) {
i += 1;
n = n * 10 + (s.charAt(i) - '0');
}
if (curr != null) {
Integer prev = ints.removeLast();
ints.addLast(calc(prev, n, curr));
curr = null;
} else {
ints.addLast(n);
}
} else if (ch != ' ') {
if (ch == '-' || ch == '+') {
ops.addLast(ch);
} else {
curr = ch;
}
}
}
while (!ops.isEmpty()) {
Integer i1 = ints.removeFirst();
Integer i2 = ints.removeFirst();
Character op = ops.removeFirst();
ints.addFirst(calc(i1, i2, op));
}
return ints.pop();
}
private Integer calc(Integer i1, Integer i2, Character op) {
switch (op) {
case '+':
return i1 + i2;
case '-':
return i1 - i2;
case '*':
return i1 * i2;
case '/':
return i1 / i2;
}
return null;
}
}
}