UVA 10125 Sumsets

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long LL;
 4 struct Node {
 5     LL val;
 6     int x,y;
 7     Node(LL v,int a,int b):val(v),x(a),y(b) {}
 8     bool operator<(const Node &t) const {
 9         return val < t.val;
10     }
11     bool operator>(const Node &t) const {
12         return val > t.val;
13     }
14     bool operator!=(const Node &t) const {
15         return x != t.x && y != t.y && x != t.y && y != t.x;
16     }
17 };
18 vector<Node>a,b;
19 LL d[1010];
20 int main() {
21     ios::sync_with_stdio(false);
22     int n;
23     while(cin>>n && n) {
24         for(int i = 0; i < n; ++i) cin>>d[i];
25         a.clear();
26         b.clear();
27         for(int i = 0; i < n; ++i)
28             for(int j = i + 1; j < n; ++j) {
29                 a.push_back(Node(d[i] + d[j],i,j));
30                 b.push_back(Node(d[i] - d[j],i,j));
31                 b.push_back(Node(d[j] - d[i],j,i));
32             }
33         sort(a.begin(),a.end());
34         sort(b.begin(),b.end());
35         LL ret;
36         memset(&ret,0x80,sizeof(LL));
37         for(auto it = a.begin(); it != a.end(); ++it){
38             auto lvalue = lower_bound(b.begin(),b.end(),*it);
39             auto rvalue = upper_bound(lvalue,b.end(),*it);
40             for(;lvalue != rvalue; ++lvalue)
41                 if(*lvalue != *it)
42                     ret = max(ret,it->val + d[lvalue->y]);
43         }
44         if (ret < -536870912)
45             cout<<"no solution"<<endl;
46         else cout<<ret<<endl;
47     }
48     return 0;
49 }
50 /*
51 5
52 2
53 3
54 5
55 7
56 12
57 */