经典问题——输出n对括号的所有组合

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<string>
 4 using namespace std;
 5 
 6 int n;
 7 
 8 void general(int n,int l,int r,int& num,string res)
 9 {
10     if (r == n)
11     {
12         num++;
13         cout << res << endl;
14         return;
15     }
16     if (l == r)
17     {
18         l++;
19         res = res + ‘(‘;
20         general(n, l, r, num, res);
21     }
22     else
23     {
24         if (l != n)
25         {
26             l++;
27             res = res + ‘(‘;
28             general(n, l, r, num, res);
29 
30             res.pop_back();
31             l--;
32             r++;
33             res = res + ‘)‘;
34             general(n, l, r, num, res);
35         }
36         else
37         {
38             r++;
39             res = res + ‘)‘;
40             general(n, l, r, num, res);
41         }
42     }
43     return;
44 }
45 
46 int main()
47 {
48     string str;
49     int num;
50     while (scanf("%d",&n) == 1)
51     {
52         num = 0;
53         general(n, 0, 0, num, str);
54         printf("%d\n", num);
55     }
56     return 0;
57 }