【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。

  1 /* 3016 */
  2 #include <iostream>
  3 #include <string>
  4 #include <map>
  5 #include <queue>
  6 #include <set>
  7 #include <stack>
  8 #include <vector>
  9 #include <deque>
 10 #include <algorithm>
 11 #include <cstdio>
 12 #include <cmath>
 13 #include <ctime>
 14 #include <cstring>
 15 #include <climits>
 16 #include <cctype>
 17 #include <cassert>
 18 #include <functional>
 19 #include <iterator>
 20 #include <iomanip>
 21 using namespace std;
 22 //#pragma comment(linker,"/STACK:102400000,1024000")
 23
 24 #define sti                set<int>
 25 #define stpii            set<pair<int, int> >
 26 #define mpii            map<int,int>
 27 #define vi                vector<int>
 28 #define pii                pair<int,int>
 29 #define vpii            vector<pair<int,int> >
 30 #define rep(i, a, n)     for (int i=a;i<n;++i)
 31 #define per(i, a, n)     for (int i=n-1;i>=a;--i)
 32 #define clr                clear
 33 #define pb                 push_back
 34 #define mp                 make_pair
 35 #define fir                first
 36 #define sec                second
 37 #define all(x)             (x).begin(),(x).end()
 38 #define SZ(x)             ((int)(x).size())
 39 #define lson            l, mid, rt<<1
 40 #define rson            mid+1, r, rt<<1|1
 41
 42 typedef struct {
 43     int v, w, nxt;
 44 } edge_t;
 45
 46 typedef struct node_t {
 47     int h, xl, xr, w;
 48
 49     node_t() {}
 50
 51     friend bool operator< (const node_t& a, const node_t& b) {
 52         return a.h < b.h;
 53     }
 54
 55 } node_t;
 56
 57 const int BASE = 1001;
 58 const int maxn = 1e5+5;
 59 const int maxv = 1e5+5;
 60 const int maxe = 5e5+5;
 61 node_t nd[maxv];
 62 bool mark[maxn<<2];
 63 int ID[maxn<<2];
 64 int X[maxn];
 65 edge_t E[maxe];
 66 int head[maxv];
 67 int dis[maxv];
 68 bool visit[maxv];
 69 int m;
 70
 71 void init() {
 72     memset(head, -1, sizeof(head));
 73     m = 0;
 74 }
 75
 76 void addEdge(int u, int v, int w) {
 77     E[m].v = v;
 78     E[m].w = w;
 79     E[m].nxt = head[u];
 80     head[u] = m++;
 81 }
 82
 83 inline void PushDown(int rt) {
 84     if (mark[rt]) {
 85         ID[rt<<1] = ID[rt<<1|1] = ID[rt];
 86         mark[rt<<1] = mark[rt<<1|1] = true;
 87         mark[rt] = false;
 88     }
 89 }
 90
 91 void Build(int l, int r, int rt) {
 92     mark[rt] = true;
 93     ID[rt] = 0;
 94     if (l == r)
 95         return ;
 96
 97     int mid = (l + r) >> 1;
 98     Build(lson);
 99     Build(rson);
100 }
101
102 void Update(int L, int R, int id, int l, int r, int rt) {
103     if (L<=l && R>=r) {
104         ID[rt] = id;
105         mark[rt] = true;
106         return ;
107     }
108
109     PushDown(rt);
110     int mid = (l + r) >> 1;
111
112     if (L > mid) {
113         Update(L, R, id, rson);
114     } else if (R <= mid) {
115         Update(L, R, id, lson);
116     } else {
117         Update(L, R, id, lson);
118         Update(L, R, id, rson);
119     }
120 }
121
122 int Query(int x, int l, int r, int rt) {
123     if (l == r)
124         return ID[rt];
125
126     PushDown(rt);
127     int mid = (l + r) >> 1;
128
129     if (x <= mid)
130         return Query(x, lson);
131     else
132         return Query(x, rson);
133 }
134
135 int spfa(int s, int t) {
136     queue<int> Q;
137     int u, v, k;
138
139     memset(dis, 0, sizeof(dis));
140     memset(visit, false, sizeof(visit));
141     dis[s] = 100;
142     visit[s] = true;
143     Q.push(s);
144
145     while (!Q.empty()) {
146         u = Q.front();
147         Q.pop();
148         visit[u] = false;
149         for (k=head[u]; k!=-1; k=E[k].nxt) {
150             v = E[k].v;
151             if (dis[u]+E[k].w > dis[v]) {
152                 dis[v] = dis[u] + E[k].w;
153                 if (!visit[v]) {
154                     visit[v] = true;
155                     Q.push(v);
156                 }
157             }
158         }
159     }
160
161     int ret = (dis[t]==0) ? -1 : dis[t];
162     return ret;
163 }
164
165 int main() {
166     ios::sync_with_stdio(false);
167     #ifndef ONLINE_JUDGE
168         freopen("data.in", "r", stdin);
169         freopen("data.out", "w", stdout);
170     #endif
171
172     int n;
173     int lid;
174     int rid;
175     int ans;
176     int src, des;
177
178     while (scanf("%d", &n) != EOF) {
179         memset(visit, false, sizeof(visit));
180         rep(i, 1, n+1) {
181             scanf("%d %d %d %d", &nd[i].h, &nd[i].xl, &nd[i].xr, &nd[i].w);
182             visit[nd[i].xl] = visit[nd[i].xr] = true;
183         }
184         sort(nd+1, nd+1+n);
185         if (nd[n].w <= -100) {
186             puts("-1");
187             continue;
188         }
189         int nx = 0;
190         rep(i, 0, maxn) {
191             if (visit[i])
192                 X[i] = ++nx;
193         }
194         src = 0;
195         des = n+1;
196
197         init();
198         Build(1, nx, 1);
199         Update(X[nd[1].xl], X[nd[1].xr], 1, 1, nx, 1);
200         addEdge(1, des, 0);
201         rep(i, 2, n+1) {
202             lid = Query(X[nd[i].xl], 1, nx, 1);
203             if (lid)
204                 addEdge(i, lid, nd[lid].w);
205             else
206                 addEdge(i, des, 0);
207             rid = Query(X[nd[i].xr], 1, nx, 1);
208             if (rid) {
209                 if (lid != rid)
210                     addEdge(i, rid, nd[rid].w);
211             } else {
212                 addEdge(i, des, 0);
213             }
214             Update(X[nd[i].xl], X[nd[i].xr], i, 1, nx, 1);
215         }
216         addEdge(src, n, nd[n].w);
217
218         ans = spfa(src, des);
219         printf("%d\n", ans);
220     }
221
222     #ifndef ONLINE_JUDGE
223         printf("time = %d.\n", (int)clock());
224     #endif
225
226     return 0;
227 }