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：

#include <map>
#include <set>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <string>
#include <vector>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;
#define rep(i,a,n) for (int i=a;i<=n;i++)
#define per(i,a,n) for (int i=n;i>=a;i--)
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef long long ll;
typedef pair<int, int> PII;
const ll mod = 1000000007;
const int inf = 0x3f3f3f3f;
const double eps = 1e-7;
// head

const int maxn = 1e5 + 7;

struct Ring {
    int a, b;
    ll h;
    bool operator < (Ring r) {
        if (b == r.b) return a < r.a;
        return b < r.b;
    }
}r[maxn];

int main() {
    int n;
    cin >> n;
    rep(i, 1, n) cin >> r[i].a >> r[i].b >> r[i].h;
    sort(r + 1, r + 1 + n);
    stack<Ring> ms;
    ll ans = 0, sum = 0;
    per(i, 1, n) {
        while (1) {
            if (ms.empty()) break;
            if (ms.top().b >= r[i].b && ms.top().a < r[i].b) break;
            sum -= ms.top().h;
            ms.pop();
        }
        ms.push(r[i]);
        sum += r[i].h;
        ans = max(ans, sum);
    }
    cout << ans << endl;
    return 0;
}