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| 1 | +#include <ctype.h> |
1 | 2 | #include <stdio.h> |
2 | 3 | #include <stdlib.h> |
3 | 4 |
|
4 | | -static int calculator(char *s) |
| 5 | + |
| 6 | +static int dfs(char **input) |
5 | 7 | { |
6 | | - int n; |
7 | | - int pos1 = 0; |
8 | | - int pos2 = 0; |
9 | | - int*nums = malloc(1000*sizeof(int)); |
10 | | - char *signs = malloc(1000*sizeof(char)); |
| 8 | + int i, res=0; |
| 9 | + int num = 0; |
| 10 | + int stk[700], pos = 0; |
| 11 | + charsign = '+'; |
| 12 | + char *s = *input; |
11 | 13 |
|
12 | | - nums[pos1++] = 0; |
13 | 14 | while (*s != '0円') { |
14 | | - switch (*s) { |
15 | | - case '+': |
16 | | - case '-': |
17 | | - case '(': |
18 | | - signs[pos2++] = *s; |
19 | | - break; |
20 | | - case ')': |
21 | | - --pos2; |
22 | | - if (pos1 >= 2 && pos2 > 0 && signs[pos2 - 1] != '(') { |
23 | | - n = nums[--pos1]; |
24 | | - int a = nums[--pos1]; |
25 | | - if (signs[--pos2] == '+') { |
26 | | - n = a + n; |
27 | | - } else { |
28 | | - n = a - n; |
29 | | - } |
30 | | - } |
31 | | - nums[pos1++] = n; |
32 | | - break; |
33 | | - case ' ': |
34 | | - break; |
35 | | - default: |
36 | | - n = 0; |
37 | | - while(*s >= '0' && *s <= '9') { |
38 | | - n = n * 10 + (*s - '0'); |
39 | | - s++; |
40 | | - } |
41 | | - s--; |
| 15 | + char c = *s++; |
| 16 | + if (isdigit(c)) { |
| 17 | + num = 10 * num + (c - '0'); |
| 18 | + } |
| 19 | + |
| 20 | + if (c == '(') { |
| 21 | + /* dfs("2*(1+3)") = 2 * dfs("1+3") */ |
| 22 | + num = dfs(&s); |
| 23 | + } |
42 | 24 |
|
43 | | - if (pos1 >= 2 && signs[pos2 - 1] != '(' && signs[pos2 - 1] != '(') { |
44 | | - int a = nums[--pos1]; |
45 | | - if (signs[--pos2] == '+') { |
46 | | - n = a + n; |
47 | | - } else { |
48 | | - n = a - n; |
49 | | - } |
| 25 | + if (!isdigit(c) && c != ' ' || *s == '0円') { |
| 26 | + switch (sign) { |
| 27 | + case '+': |
| 28 | + stk[pos++] = num; |
| 29 | + break; |
| 30 | + case '-': |
| 31 | + stk[pos++] = -num; |
| 32 | + break; |
| 33 | + case '*': |
| 34 | + stk[pos - 1] *= num; |
| 35 | + break; |
| 36 | + case '/': |
| 37 | + stk[pos - 1] /= num; |
| 38 | + break; |
50 | 39 | } |
51 | | - nums[pos1++] = n; |
52 | | - break; |
| 40 | + /* update the sign and reset the number */ |
| 41 | + sign = c; |
| 42 | + num = 0; |
53 | 43 | } |
54 | | - s++; |
| 44 | + |
| 45 | + /* return from the dfs */ |
| 46 | + if (c == ')') |
| 47 | + break; |
| 48 | + } |
| 49 | + |
| 50 | + /* update position */ |
| 51 | + *input = s; |
| 52 | + |
| 53 | + while (pos > 0) { |
| 54 | + res += stk[--pos]; |
55 | 55 | } |
56 | 56 |
|
57 | | - return n; |
| 57 | + return res; |
| 58 | +} |
| 59 | + |
| 60 | +static int calculator(char *s) |
| 61 | +{ |
| 62 | + return dfs(&s); |
58 | 63 | } |
59 | 64 |
|
60 | 65 | int main(int argc, char **argv) |
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