CF597C Subsequences 树状数组 + 动态规划

设$f(i, j)$表示以$i$结尾的，长为$j$的上升子序列的数量

转移时用树状数组维护即可

复杂度为$O(kn \log n)$

注：特判0

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
namespace remoon {
    #define ri register int
    #define ll long long
    #define tpr template <typename ra>
    #define rep(iu, st, ed) for(ri iu = st; iu <= ed; iu ++)
    #define drep(iu, ed, st) for(ri iu = ed; iu >= st; iu --)
    #define gc getchar
    inline int read() {
        int p = , w = ; char c = gc();
        while(c > '' || c < '') { if(c == '-') w = -; c = gc(); }
        while(c >= '' && c <= '') p = p *  + c - '', c = gc();
        return p * w;
    }
    int wr[], rw;
    #define pc(iw) putchar(iw)
    tpr inline void write(ra o, char c = '\n') {
        if(!o) pc('');
        if(o < ) o = -o, pc('-');
        while(o) wr[++ rw] = o % , o /= ;
        while(rw) pc(wr[rw --] + '');
        pc(c);
    }
}
using namespace std;
using namespace remoon;

#define sid 100050

int n, k, a[sid];
ll t[sid][];

inline void upd(int o, ll v, int k) {
    for(ri i = o; i <= n + ; i += i & (-i))
        t[i][k] += v;
}

inline ll qry(int o, int k) {
    ll ret = ;
    for(ri i = o; i; i -= i & (-i))
        ret += t[i][k];
    return ret;
}

inline void DP() {
    ll ans = ;
    if(k == ) ans = ;
    rep(i, , n) {
        upd(a[i], , );
        rep(j, , k + ) {
            ll S = qry(a[i] - , j - );
            if(j == k + ) { ans += S; break; }
            upd(a[i], S, j);
        }
    }
    write(ans);
}

int main() {
    n = read(); k = read();
    rep(i, , n) a[i] = read() + ;
    DP();
    return ;
}