-
Notifications
You must be signed in to change notification settings - Fork 22
Expand file tree
/
Copy path224.basic-calculator.cpp
More file actions
130 lines (116 loc) · 3.03 KB
/
224.basic-calculator.cpp
File metadata and controls
130 lines (116 loc) · 3.03 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
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
// Tag: Math, String, Stack, Recursion
// Time: O(N)
// Space: O(N)
// Ref: -
// Note: -
// Given a string s representing a valid expression, implement a basic calculator to evaluate it, and return the result of the evaluation.
// Note: You are not allowed to use any built-in function which evaluates strings as mathematical expressions, such as eval().
//
// Example 1:
//
// Input: s = "1 + 1"
// Output: 2
//
// Example 2:
//
// Input: s = " 2-1 + 2 "
// Output: 3
//
// Example 3:
//
// Input: s = "(1+(4+5+2)-3)+(6+8)"
// Output: 23
//
//
// Constraints:
//
// 1 <= s.length <= 3 * 105
// s consists of digits, '+', '-', '(', ')', and ' '.
// s represents a valid expression.
// '+' is not used as a unary operation (i.e., "+1" and "+(2 + 3)" is invalid).
// '-' could be used as a unary operation (i.e., "-1" and "-(2 + 3)" is valid).
// There will be no two consecutive operators in the input.
// Every number and running calculation will fit in a signed 32-bit integer.
//
//
class Solution {
public:
int calculate(string s) {
int num = 0;
int res = 0;
int sign = 1;
stack<int> st;
for (auto ch: s) {
if (isdigit(ch)) {
num = num * 10 + (ch - '0');
} else if (ch == '+' || ch == '-') {
res += num * sign;
sign = ch == '+' ? 1 : -1;
num = 0;
} else if (ch == '(') {
st.push(res);
st.push(sign);
res = 0;
sign = 1;
} else if (ch == ')') {
res += num * sign;
num = 0;
res *= st.top();
st.pop();
res += st.top();
st.pop();
}
}
return res + num * sign;
}
};
class Solution {
public:
int calculate(string s) {
int i = 0;
s = s + "+";
return cal(s, i);
}
int cal(string &s, int &i) {
int n = s.size();
int pre = 0;
int cur = 0;
char op = '\0';
while (i < n) {
while (s[i] == ' '){ i++; }
int num = 0;
int sign = 1;
if (s[i] == '-') {
sign = -1;
i++;
}
while (isdigit(s[i])) {
cout << s[i] << endl;
num = num * 10 + (s[i] - '0');
i++;
}
while (s[i] == ' '){ i++; }
if (s[i] == '(') {
i++;
num = cal(s, i);
}
num = num * sign;
if (op == '\0') {
cur = num;
} else if (op == '+') {
pre = pre + cur;
cur = num;
} else if (op == '-') {
pre = pre + cur;
cur = -num;
}
if (s[i] == ')') {
i++;
return pre + cur;
}
op = s[i];
i++;
}
return pre + cur;
}
};