Codeforces Round #401 (Div. 2) E. Hanoi Factory 栈
E. Hanoi Factory
链接：
http://codeforces.com/contest/777/problem/E
题解：
排序b从小到大，在b相同排序a从小到大，使其满足如果i-1不能取，那么i-2也不能取，
这样从后往前推入栈，如果不满足推出栈直到满足再推入栈，每次推入的答案记录最大值即可。
代码：
1 #include <map> 2 #include <set> 3 #include <cmath> 4 #include <queue> 5 #include <stack> 6 #include <cstdio> 7 #include <string> 8 #include <vector> 9 #include <cstring> 10 #include <iostream> 11 #include <algorithm> 12 #include <functional> 13 using namespace std; 14 #define rep(i,a,n) for (int i=a;i<=n;i++) 15 #define per(i,a,n) for (int i=n;i>=a;i--) 16 #define pb push_back 17 #define mp make_pair 18 #define all(x) (x).begin(),(x).end() 19 #define fi first 20 #define se second 21 #define SZ(x) ((int)(x).size()) 22 typedef vector<int> VI; 23 typedef long long ll; 24 typedef pair<int, int> PII; 25 const ll mod = 1000000007; 26 const int inf = 0x3f3f3f3f; 27 const double eps = 1e-7; 28 // head 29 30 const int maxn = 1e5 + 7; 31 32 struct Ring { 33 int a, b; 34 ll h; 35 bool operator < (Ring r) { 36 if (b == r.b) return a < r.a; 37 return b < r.b; 38 } 39 }r[maxn]; 40 41 int main() { 42 int n; 43 cin >> n; 44 rep(i, 1, n) cin >> r[i].a >> r[i].b >> r[i].h; 45 sort(r + 1, r + 1 + n); 46 stack<Ring> ms; 47 ll ans = 0, sum = 0; 48 per(i, 1, n) { 49 while (1) { 50 if (ms.empty()) break; 51 if (ms.top().b >= r[i].b && ms.top().a < r[i].b) break; 52 sum -= ms.top().h; 53 ms.pop(); 54 } 55 ms.push(r[i]); 56 sum += r[i].h; 57 ans = max(ans, sum); 58 } 59 cout << ans << endl; 60 return 0; 61 }
