codeforces test #12 C. Subsequences 树状数组统计

C. Subsequences

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

For the given sequence with n different elements find the number of increasing subsequences with k + 1 elements. It is guaranteed that the answer is not greater than 8·1018.

Input

First line contain two integer values n and k (1 ≤ n ≤ 105, 0 ≤ k ≤ 10) — the length of sequence and the number of elements in increasing subsequences.

Next n lines contains one integer ai (1 ≤ ai ≤ n) each — elements of sequence. All values ai are different.

Output

Print one integer — the answer to the problem.

Sample test(s)

input

5 2
1
2
3
5
4

output

7

#include<bits/stdc++.h>
#define REP(i,a,b) for(int i=a;i<=b;i++)
#define MS0(a) memset(a,0,sizeof(a))

using namespace std;

typedef long long ll;
const int maxn=100100;
const int INF=(1<<29);

int n,k;
ll a[maxn];
ll c[maxn][15];

int lowbit(int x)
{
    return x&(-x);
}

ll sum(int p,int id)
{
    ll res=0;
    while(p>0){
        res+=c[p][id];
        p-=lowbit(p);
    }
    return res;
}

void add(int p,int id,ll x)
{
    while(p<=n){
        c[p][id]+=x;
        p+=lowbit(p);
    }
}

int main()
{
    ///freopen("in.txt","r",stdin);
    while(cin>>n>>k){
        REP(i,1,n) scanf("%I64d",&a[i]);
        MS0(c);
        REP(i,1,n){
            add(a[i],1,1);
            REP(j,2,k+1) add(a[i],j,sum(a[i]-1,j-1));
        }
        cout<<sum(n,k+1)<<endl;
    }
    return 0;
}
→Judgement Protocol