【HDOJ】3016 Man Down

线段树+spfa求最长路。
逆向思维，从最底下一块板子建图。需要注意的是任何一个板子掉落下面再无板子，此时都可以看做一个终结状态。

/* 3016 */
#include <iostream>
#include <string>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>
#include <deque>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <climits>
#include <cctype>
#include <cassert>
#include <functional>
#include <iterator>
#include <iomanip>
using namespace std;
//#pragma comment(linker,"/STACK:102400000,1024000")

#define sti                set<int>
#define stpii            set<pair<int, int> >
#define mpii            map<int,int>
#define vi                vector<int>
#define pii                pair<int,int>
#define vpii            vector<pair<int,int> >
#define rep(i, a, n)     for (int i=a;i<n;++i)
#define per(i, a, n)     for (int i=n-1;i>=a;--i)
#define clr                clear
#define pb                 push_back
#define mp                 make_pair
#define fir                first
#define sec                second
#define all(x)             (x).begin(),(x).end()
#define SZ(x)             ((int)(x).size())
#define lson            l, mid, rt<<1
#define rson            mid+1, r, rt<<1|1

typedef struct {
    int v, w, nxt;
} edge_t;

typedef struct node_t {
    int h, xl, xr, w;
    
    node_t() {}
    
    friend bool operator< (const node_t& a, const node_t& b) {
        return a.h < b.h;
    }
    
} node_t;

const int BASE = 1001;
const int maxn = 1e5+5;
const int maxv = 1e5+5;
const int maxe = 5e5+5;
node_t nd[maxv];
bool mark[maxn<<2];
int ID[maxn<<2];
int X[maxn];
edge_t E[maxe];
int head[maxv];
int dis[maxv];
bool visit[maxv];
int m;

void init() {
    memset(head, -1, sizeof(head));
    m = 0;
}

void addEdge(int u, int v, int w) {
    E[m].v = v;
    E[m].w = w;
    E[m].nxt = head[u];
    head[u] = m++;
}

inline void PushDown(int rt) {
    if (mark[rt]) {
        ID[rt<<1] = ID[rt<<1|1] = ID[rt];
        mark[rt<<1] = mark[rt<<1|1] = true;
        mark[rt] = false;
    }
}

void Build(int l, int r, int rt) {
    mark[rt] = true;
    ID[rt] = 0;
    if (l == r)
        return ;
    
    int mid = (l + r) >> 1;
    Build(lson);
    Build(rson);
}

void Update(int L, int R, int id, int l, int r, int rt) {
    if (L<=l && R>=r) {
        ID[rt] = id;
        mark[rt] = true;
        return ;
    }
    
    PushDown(rt);
    int mid = (l + r) >> 1;
    
    if (L > mid) {
        Update(L, R, id, rson);
    } else if (R <= mid) {
        Update(L, R, id, lson);
    } else {
        Update(L, R, id, lson);
        Update(L, R, id, rson);
    }
}

int Query(int x, int l, int r, int rt) {
    if (l == r)
        return ID[rt];
    
    PushDown(rt);
    int mid = (l + r) >> 1;
    
    if (x <= mid)
        return Query(x, lson);
    else
        return Query(x, rson);
}

int spfa(int s, int t) {
    queue<int> Q;
    int u, v, k;
    
    memset(dis, 0, sizeof(dis));
    memset(visit, false, sizeof(visit));
    dis[s] = 100;
    visit[s] = true;
    Q.push(s);
    
    while (!Q.empty()) {
        u = Q.front();
        Q.pop();
        visit[u] = false;
        for (k=head[u]; k!=-1; k=E[k].nxt) {
            v = E[k].v;
            if (dis[u]+E[k].w > dis[v]) {
                dis[v] = dis[u] + E[k].w;
                if (!visit[v]) {
                    visit[v] = true;
                    Q.push(v);
                }
            }
        }
    }
    
    int ret = (dis[t]==0) ? -1 : dis[t];
    return ret;
}

int main() {
    ios::sync_with_stdio(false);
    #ifndef ONLINE_JUDGE
        freopen("data.in", "r", stdin);
        freopen("data.out", "w", stdout);
    #endif
    
    int n;
    int lid;
    int rid;
    int ans;
    int src, des;
    
    while (scanf("%d", &n) != EOF) {
        memset(visit, false, sizeof(visit));
        rep(i, 1, n+1) {
            scanf("%d %d %d %d", &nd[i].h, &nd[i].xl, &nd[i].xr, &nd[i].w);
            visit[nd[i].xl] = visit[nd[i].xr] = true;
        }
        sort(nd+1, nd+1+n);
        if (nd[n].w <= -100) {
            puts("-1");
            continue;
        }
        int nx = 0;
        rep(i, 0, maxn) {
            if (visit[i])
                X[i] = ++nx;
        }
        src = 0;
        des = n+1;
        
        init();
        Build(1, nx, 1);
        Update(X[nd[1].xl], X[nd[1].xr], 1, 1, nx, 1);
        addEdge(1, des, 0);
        rep(i, 2, n+1) {
            lid = Query(X[nd[i].xl], 1, nx, 1);
            if (lid)
                addEdge(i, lid, nd[lid].w);
            else
                addEdge(i, des, 0);
            rid = Query(X[nd[i].xr], 1, nx, 1);
            if (rid) {
                if (lid != rid)
                    addEdge(i, rid, nd[rid].w);
            } else {
                addEdge(i, des, 0);
            }
            Update(X[nd[i].xl], X[nd[i].xr], i, 1, nx, 1);
        }
        addEdge(src, n, nd[n].w);
        
        ans = spfa(src, des);
        printf("%d
", ans);
    }
    
    #ifndef ONLINE_JUDGE
        printf("time = %d.
", (int)clock());
    #endif
    
    return 0;
}