-
Notifications
You must be signed in to change notification settings - Fork 3
Expand file tree
/
Copy pathCalculaorII.java
More file actions
79 lines (67 loc) · 2.41 KB
/
CalculaorII.java
File metadata and controls
79 lines (67 loc) · 2.41 KB
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
66
67
68
69
70
71
72
73
74
75
76
77
78
79
public class CalculatorII {
public int cal(int x, int y, char op) {
if(op == '+') {
return x + y;
} else {
return x - y;
}
}
public boolean hasPrecedence(char op1, char op2) {
if (op2 == '(' || op2 == ')')
return false;
if ((op1 == '*' || op1 == '/'))
return false;
else
return true;
}
public int calculate(String s) {
if(s == null || s.length() == 0) return 0;
char[] cs = s.trim().toCharArray();
int n = cs.length;
int i = 0;
LinkedList<Integer> numsStack = new LinkedList<Integer> ();
LinkedList<Character> opsStack = new LinkedList<Character> ();
while(i < n) {
if(cs[i] >= '0' && cs[i] <= '9') {
StringBuffer e = new StringBuffer();
while(i < n && cs[i] >= '0' && cs[i] <= '9') {
e.append(cs[i++]);
}
numsStack.addFirst(Integer.parseInt(e.toString()));
}
else if(cs[i] == ' ') {
++i;
}
else if(cs[i] == '(') {
opsStack.addFirst(cs[i++]);
}
else if(cs[i] == ')') {
while(opsStack.peekFirst() != '(') {
int n2 = numsStack.pollFirst();
int n1 = numsStack.pollFirst();
char op = opsStack.pollFirst();
numsStack.addFirst(cal(n1, n2, op));
}
opsStack.pollFirst();
++i;
}
/** when cs[i] is '+' or '-' or '*' or '/' */
else {
while(!opsStack.isEmpty() && hasPrecedence(cs[i], opsStack.peekFirst())) {
int n2 = numsStack.pollFirst();
int n1 = numsStack.pollFirst();
char op = opsStack.pollFirst();
numsStack.addFirst(cal(n1, n2, op));
}
opsStack.addFirst(cs[i++]);
}
}
while(!opsStack.isEmpty()) {
int n2 = numsStack.pollFirst();
int n1 = numsStack.pollFirst();
char op = opsStack.pollFirst();
numsStack.addFirst(cal(n1, n2, op));
}
return numsStack.pollFirst();
}
}