POJ 2104 - K-th Number 【开坑!

先来朴素的排序解法：

 1 #include <cstdio>
 2 #include <algorithm>
 3 using namespace std;
 4 
 5 struct D {
 6     int pos, val;
 7 } sorted[100000];
 8 
 9 int cmp(const struct D &a, const struct D &b)
10 {
11     return a.val < b.val;
12 }
13 
14 int main(void)
15 {
16     int N, M;
17     scanf("%d%d", &N, &M);
18     for(int i=0; i<N; ++i) {
19         scanf("%d", &sorted[i].val);
20         sorted[i].pos = i + 1;
21     }
22     sort(sorted, sorted + N, cmp);
23 
24     for(int c=0; c<M; ++c) {
25         int i, j, k;
26         scanf("%d%d%d", &i, &j, &k);
27         int u;
28         for(u=0; u<N; ++u)
29             if (sorted[u].pos >= i && sorted[u].pos <= j)
30                 if (!--k) break;
31         printf("%d\n", sorted[u].val);
32     }
33     return 0;
34 }

 

2104 Accepted 1140K 6625MS G++ 605B 2014-07-24 11:06:26

 

然后特地学了主席树（还不会套树状数组）：

 1 #include <cstdio>
 2 #include <algorithm>
 3 using namespace std;
 4 
 5 #define MAXN    100007
 6 
 7 int a[MAXN], mapa[MAXN], QN;
 8 
 9 int lsi[MAXN*100], rsi[MAXN*100], v[MAXN*100], totv;
10 
11 #define lsn        l, m
12 #define rsn        m+1, r
13 
14 int build(int l, int r)
15 {
16     int root = totv++;
17     v[root] = 0;
18     if (l == r) {
19         lsi[root] = rsi[root] = 0;
20         return root;
21     }
22     int m = (l + r) >> 1;
23     build(lsn); build(rsn);
24     return root;
25 }
26 
27 int lshift(int T, int p)
28 {
29     int root, t;
30     root = t = totv++;
31     int l = 0, r = QN - 1;
32     while(l < r) {
33         v[t] = v[T] + 1;
34         int m = (l+r) >> 1;
35         if (p <= m) {
36             lsi[t] = totv++, rsi[t] = rsi[T];
37             T = lsi[T], t = lsi[t], r = m;
38         } else {
39             rsi[t] = totv++, lsi[t] = lsi[T];
40             T = rsi[T], t = rsi[t], l = m + 1;
41         }
42     }
43     v[t] = v[T] + 1;
44     return root;
45 }
46 
47 int query(int Tl, int Tr, int k)
48 {
49     int l = 0, r = QN-1;
50     while(l < r) {
51         int m = (l+r) >> 1;
52         if (v[lsi[Tl]] - v[lsi[Tr]] >= k)
53             Tl = lsi[Tl], Tr = lsi[Tr], r = m;
54         else {
55             k -= v[lsi[Tl]] - v[lsi[Tr]];
56             Tl = rsi[Tl], Tr = rsi[Tr], l = m+1;
57         }
58     }
59     return l;
60 }
61 
62 int T[MAXN + 1];
63 
64 int main(void)
65 {
66     int N, M;
67     scanf("%d%d", &N, &M);
68     for(int i=0;i<N; ++i) {
69         scanf("%d", &a[i]);
70         mapa[i] = a[i];
71     }
72     sort(mapa, mapa + N);
73     QN = unique(mapa, mapa + N) - mapa;
74     T[N] = build(0, QN-1);
75     for(int i=N; i-->0;) {
76         a[i] = lower_bound(mapa, mapa + QN, a[i]) - mapa;
77         T[i] = lshift(T[i+1], a[i]);
78     }
79     for(int u=0; u<M; ++u) {
80         int i, j, k;
81         scanf("%d%d%d", &i, &j, &k);
82         printf("%d\n", mapa[query(T[i-1], T[j], k)]);
83     }
84     return 0;
85 }

 

2104 Accepted 24700K 1610MS G++ 1577B 2014-07-24 14:05:17

看到时间差距了？

posted @ 2014-07-24 11:10  e0e1e  阅读(144)  评论(0)  编辑  收藏  举报