4月27日 Removal 删除若干个数后的子序列个数

#include<bits/stdc++.h>
#define LL long long
using namespace std;

int a[100005], w[15], f[100005][15];
const int mod=1e9+7;
int main(){
    int n, m, k;
    while(~scanf("%d%d%d", &n, &m, &k)){
        for(int i=1; i<=n; i++){
            scanf("%d", &a[i]);
        }
        memset(w, 0, sizeof(w));
        f[0][0]=1;
        for(int i=1; i<=n; i++){

            for(int j=0; j<=m; j++){
                if(j==0) f[i][j]=f[i-1][j];
                else f[i][j]=(f[i-1][j]+f[i-1][j-1])%mod;
                if(w[a[i]]){
                    if(i-w[a[i]]<=j){
                        f[i][j]=((f[i][j]-f[w[a[i]]-1][j-(i-w[a[i]])])+mod)%mod;
                    }
                }
                //cout<<i<<" "<<j<<" : "<<f[i][j]<<endl;
            }
            w[a[i]]=i;
        }
        printf("%d\n", f[n][m]);
    }

    return 0;
}