【HDOJ】4366 Successor

基本思路是将树形结构转换为线性结构。然后，所求即为一个区间内大于abi的最大的loy指向的ID。
将结点按照abi降序排序，注意abi可能相等。
然后，使用线段树单点更新，区间查询可解。

  1 /* 4366 */
  2 #include <iostream>
  3 #include <sstream>
  4 #include <string>
  5 #include <map>
  6 #include <queue>
  7 #include <set>
  8 #include <stack>
  9 #include <vector>
 10 #include <deque>
 11 #include <algorithm>
 12 #include <cstdio>
 13 #include <cmath>
 14 #include <ctime>
 15 #include <cstring>
 16 #include <climits>
 17 #include <cctype>
 18 #include <cassert>
 19 #include <functional>
 20 #include <iterator>
 21 #include <iomanip>
 22 using namespace std;
 23 //#pragma comment(linker,"/STACK:102400000,1024000")
 24 
 25 #define sti                set<int>
 26 #define stpii            set<pair<int, int> >
 27 #define mpii            map<int,int>
 28 #define vi                vector<int>
 29 #define pii                pair<int,int>
 30 #define vpii            vector<pair<int,int> >
 31 #define rep(i, a, n)     for (int i=a;i<n;++i)
 32 #define per(i, a, n)     for (int i=n-1;i>=a;--i)
 33 #define clr                clear
 34 #define pb                 push_back
 35 #define mp                 make_pair
 36 #define fir                first
 37 #define sec                second
 38 #define all(x)             (x).begin(),(x).end()
 39 #define SZ(x)             ((int)(x).size())
 40 #define lson            l, mid, rt<<1
 41 #define rson            mid+1, r, rt<<1|1
 42 
 43 typedef struct node_t {
 44     int abi, id;
 45     
 46     friend bool operator< (const node_t& a, const node_t& b) {
 47         return a.abi > b.abi;
 48     }
 49     
 50 } node_t;
 51 
 52 typedef struct {
 53     int v, nxt;
 54 } edge_t;
 55 
 56 const int maxv = 50005;
 57 const int maxn = 50005;
 58 int abi[maxv], loy[maxv];
 59 int head[maxv];
 60 edge_t E[maxv];
 61 int mx[maxn<<2];
 62 int ID[maxn<<2];
 63 int Beg[maxv], End[maxv], dfs_clock;
 64 node_t nd[maxn];
 65 int ans[maxn];
 66 int n, m, l;
 67 
 68 void init() {
 69     memset(head, -1, sizeof(head));
 70     l = dfs_clock = 0;
 71 }
 72 
 73 void addEdge(int u, int v) {
 74     E[l].v = v;
 75     E[l].nxt = head[u];
 76     head[u] = l++;
 77 }
 78 
 79 inline void PushUp(int rt) {
 80     int lb = rt<<1;
 81     int rb = lb|1;
 82     
 83     if (mx[lb] > mx[rb]) {
 84         mx[rt] = mx[lb];
 85         ID[rt] = ID[lb];
 86     } else {
 87         mx[rt] = mx[rb];
 88         ID[rt] = ID[rb];
 89     }
 90 }
 91 
 92 void Build(int l, int r, int rt) {
 93     mx[rt] = -1;
 94     if (l == r)
 95         return ;
 96     
 97     int mid = (l + r) >> 1;
 98     Build(lson);
 99     Build(rson);
100     
101     PushUp(rt);
102 }
103 
104 void Update(int x, int id, int val, int l, int r, int rt) {
105     if (l == r) {
106         mx[rt] = val;
107         ID[rt] = id;
108         return ;
109     }
110     
111     int mid = (l + r) >> 1;
112     
113     if (x <= mid)
114         Update(x, id, val, lson);
115     else
116         Update(x, id, val, rson);
117     
118     PushUp(rt);
119 }
120 
121 pii Query(int L, int R, int l, int r, int rt) {
122     if (L==l && R==r) {
123         return mp(mx[rt], ID[rt]);
124     }
125     
126     int mid = (l + r) >> 1;
127     
128     if (R <= mid) {
129         return Query(L, R, lson);
130     } else if (L > mid) {
131         return Query(L, R, rson);
132     } else {
133         pii ltmp = Query(L, mid, lson);
134         pii rtmp = Query(mid+1, R, rson);
135         if (ltmp.fir > rtmp.fir)
136             return ltmp;
137         else
138             return rtmp;
139     }
140 }
141 
142 void dfs(int u) {
143     int v, k;
144     
145     Beg[u] = ++dfs_clock;
146     for (k=head[u]; k!=-1; k=E[k].nxt) {
147         v = E[k].v;
148         dfs(v);
149     }
150     End[u] = dfs_clock;
151 }
152 
153 void solve() {
154     
155     dfs(0);
156     int nn = dfs_clock;
157     memset(mx, -1, sizeof(mx));
158     
159     rep(i, 1, n) {
160         nd[i-1].abi = abi[i];
161         nd[i-1].id = i;
162     }
163     
164     int mm = n - 1;
165     sort(nd, nd+mm);
166     
167     int u;
168     pii p;
169     int i = 0;
170     
171     while (i < mm) {
172         int j = i;
173         while (i<mm && nd[i].abi==nd[j].abi) {
174             u = nd[i].id;
175             int l = Beg[u]+1;
176             int r = End[u];
177             if (l > r) {
178                 ans[u] = -1;
179             } else {
180                 p = Query(l, r, 1, nn, 1);
181                 ans[u] = p.fir==-1 ? -1:p.sec;
182             }
183             ++i;
184         }
185         
186         while (j < i) {
187             u = nd[j].id;
188             Update(Beg[u], u, loy[u], 1, nn, 1);
189             ++j;
190         }
191     }
192     
193     
194     while (m--) {
195         scanf("%d", &u);
196         printf("%d
", ans[u]);
197     }
198 } 
199 
200 int main() {
201     ios::sync_with_stdio(false);
202     #ifndef ONLINE_JUDGE
203         freopen("data.in", "r", stdin);
204         freopen("data.out", "w", stdout);
205     #endif
206     
207     int t;
208     int u;
209     
210     scanf("%d", &t);
211     while (t--) {
212         init();
213         scanf("%d %d", &n, &m);
214         rep(i, 1, n) {
215             scanf("%d %d %d", &u, &loy[i], &abi[i]);
216             addEdge(u, i);
217         }
218         solve();
219     }
220     
221     #ifndef ONLINE_JUDGE
222         printf("time = %d.
", (int)clock());
223     #endif
224     
225     return 0;
226 }

数据发生器。

 1 from copy import deepcopy
 2 from random import randint, shuffle
 3 import shutil
 4 import string
 5 
 6 
 7 def GenDataIn():
 8     with open("data.in", "w") as fout:
 9         t = 10
10         fout.write("%d
" % (t))
11         for tt in xrange(t):
12             n = randint(200, 300)
13             m = randint(200, 300)
14             fout.write("%d %d
" % (n, m))
15             ust = [0]
16             st = set()
17             for i in xrange(1, n):
18                 idx = randint(0, len(ust)-1)
19                 a = ust[idx]
20                 b = randint(0, 105)
21                 while True:
22                     c = randint(0, 10**6)
23                     if c not in st:
24                         break
25                 st.add(c)
26                 fout.write("%d %d %d
" % (a, c, b))
27                 ust.append(i)
28             L = []
29             for i in xrange(m):
30                 x = randint(1, n-1)
31                 L.append(x)
32             fout.write("
".join(map(str, L)) + "
")    
33             
34 def MovDataIn():
35     desFileName = "F:eclipse_prjworkspacehdojdata.in"
36     shutil.copyfile("data.in", desFileName)
37 
38     
39 if __name__ == "__main__":
40     GenDataIn()
41     MovDataIn()