Codeforces Gym101097I：Sticks （思维）
http://codeforces.com/gym/101097/attachments
题意：现在有k种颜色的木棍，每种颜色有ni根木棍，每根木棍有一个长度，问是否有三根木棍可以组成三角形，并且这三根木棍的颜色都不相同。
思路：忘了并不能直接枚举第i根，然后找i-1和i-2根，因为还有很多情况没考虑到。
可以用三个变量，分别存储当前最大的三种颜色的最大值，然后根据新进来的颜色进行判定，进行更新。
1 #include <bits/stdc++.h> 2 using namespace std; 3 typedef long long LL; 4 #define N 5000010 5 #define INF 0x3f3f3f3f 6 struct node { 7 int id; LL val; 8 bool operator < (const node &rhs) const { 9 if(val != rhs.val) return val < rhs.val; 10 return id < rhs.id; 11 } 12 } ; 13 vector<LL> vec; 14 vector<node> p; 15 node a, b, c; 16 17 int main() { 18 freopen("sticks.in", "r", stdin); 19 freopen("sticks.out", "w", stdout); 20 int k; scanf("%d", &k); 21 int cnt = 0; 22 for(int i = 1; i <= k; i++) { 23 int n; scanf("%d", &n); 24 vec.clear(); 25 for(int j = 1; j <= n; j++) { 26 LL x; scanf("%lld", &x); 27 vec.push_back(x); 28 } 29 sort(vec.begin(), vec.end()); 30 vec.erase(unique(vec.begin(), vec.end()), vec.end()); 31 for(int j = 0; j < vec.size(); j++) p.push_back( (node) { i, vec[j] } ); 32 } 33 sort(p.begin(), p.end()); 34 bool flag = 0; 35 // a = p[1]; b = p[0]; c.id = 0, c.val = 0; 36 for(int i = 0; i < p.size() && !flag; i++) { 37 if(a.id == p[i].id) { 38 if(p[i].val < b.val + c.val) printf("%d %lld %d %lld %d %lld\n", p[i].id, p[i].val, b.id, b.val, c.id, c.val), flag = 1; 39 a = p[i]; 40 } else if(b.id == p[i].id) { 41 if(p[i].val < a.val + c.val) printf("%d %lld %d %lld %d %lld\n", p[i].id, p[i].val, a.id, a.val, c.id, c.val), flag = 1; 42 b = a; a = p[i]; 43 } else { 44 if(p[i].val < a.val + b.val) printf("%d %lld %d %lld %d %lld\n", p[i].id, p[i].val, a.id, a.val, b.id, b.val), flag = 1; 45 c = b; b = a; a = p[i]; 46 } 47 } 48 if(!flag) puts("NIE"); 49 return 0; 50 }
