-
Notifications
You must be signed in to change notification settings - Fork 13
/
lis.cpp
50 lines (50 loc) · 1.19 KB
/
lis.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
/**
* Usage lis();
* a has to be 1 based index
* number of elements in longest increasing subsequence = total number of different non-increasing subsequence
* number of elements in longest decreasing subsequence = total number of different non-decreasing subsequence
* above two facts are used vice-versa
*/
int lis(vector <int> &a) {
int inf = 2e9, n = a.size() - 1;
vector <int> a, ls, ind, par, seq;
//change initialization of ls
//for non/- incresing/decreasing seq
ls.assign(n + 1, inf);
ind.assign(n + 1, 0);
par.assign(n + 1, 0);
ls[0] = -inf;
int i,ans = 1;
for (i = 1; i <= n; ++i) {
int l = 1, r = n, pos;
while (l <= r) {
int m = (l + r) / 2;
//change below for all modification
//of non/- incresing/decreasing seq
if (ls[m] > a[i]) {
pos = m;
r = m - 1;
} else
l = m + 1;
}
//change below for all modification
//of non/- incresing/decreasing seq
if (ls[pos - 1] < a[i] && a[i] < ls[pos]) {
ls[pos] = a[i];
ind[pos] = i;
par[i] = ind[pos - 1];
ans = max(ans, pos);
}
}
if (ans == 1) {
seq.push_back(a[1]);
return 1;
}
i = ind[ans];
while (i) {
seq.push_back(a[i]);
i = par[i];
}
reverse(seq.begin(), seq.end());
return ans;
}