[luoguP1439] 排列LCS问题（DP + 树状数组）

 1 #include <cstdio>
 2 #include <algorithm>
 3 #include <cstring>
 4 
 5 using namespace std;
 6 
 7 const int MAXN = 100001;
 8 int n, ans;
 9 int a[MAXN], b[MAXN], c[MAXN];
10 
11 inline int query(int x)
12 {
13     int ans = 0;
14     for(; x; x -= x & -x) ans = max(ans, c[x]);
15     return ans;
16 }
17 
18 inline void update(int x, int d)
19 {
20     for(; x <= n; x += x & -x) c[x] = max(c[x], d);
21 }
22 
23 int main()
24 {
25     int i, j, x, y;
26     scanf("%d", &n);
27     for (i = 1; i <= n; i++) scanf("%d", &x), a[x] = i;
28     for (i = 1; i <= n; i++) scanf("%d", &x), b[i] = a[x];
29     for(i = 1; i <= n; i++)
30     {
31         y = query(b[i] - 1) + 1;
32         update(b[i], y);
33         ans = max(ans, y);
34     }
35     printf("%d", ans);
36     return 0;
37 }