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。

 #include <bits/stdc++.h>
 using namespace std;
 typedef long long LL;
 #define N 5000010
 #define INF 0x3f3f3f3f
 struct node {
     int id; LL val;
     bool operator < (const node &rhs) const {
         if(val != rhs.val) return val < rhs.val;
         return id < rhs.id;
     }
 } ;
 vector<LL> vec;
 vector<node> p;
 node a, b, c;

 int main() {
     freopen("sticks.in", "r", stdin);
     freopen("sticks.out", "w", stdout);
     int k; scanf("%d", &k);
     int cnt = ;
     for(int i = ; i <= k; i++) {
         int n; scanf("%d", &n);
         vec.clear();
         for(int j = ; j <= n; j++) {
             LL x; scanf("%lld", &x);
             vec.push_back(x);
         }
         sort(vec.begin(), vec.end());
         vec.erase(unique(vec.begin(), vec.end()), vec.end());
         for(int j = ; j < vec.size(); j++) p.push_back( (node) { i, vec[j] } );
     }
     sort(p.begin(), p.end());
     bool flag = ;
 //    a = p[1]; b = p[0]; c.id = 0, c.val = 0;
     for(int i = ; i < p.size() && !flag; i++) {
         if(a.id == p[i].id) {
             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 = ;
             a = p[i];
         } else if(b.id == p[i].id) {
             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 = ;
             b = a; a = p[i];
         } else {
             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 = ;
             c = b; b = a; a = p[i];
         }
     }
     if(!flag) puts("NIE");
     return ;
 }