题目
#include<bits/stdc++.h>
using namespace std;
#define int long long
const int maxn = 3005, mod = 1e9 + 7;
int a[maxn], b[maxn], cnt_low[maxn];//cnt_low[i]表示小于i的数字个数
int sum[maxn][maxn];//前缀和
int f[maxn][maxn];//f[i][j]表示选了i个数（不一定是原始序列的前i个），最大的数是j的方案数//转移：f[i][j] = f[i - 1][1] + f[i - 1][2] + ... + f[i - 1][j - 1](前i-1选的最大数小于j，那么第i个数就得选j) + f[i - 1][j]（第i个数在小于等于j的数字中随便选）
void init(int n, int m){for(int i = 1; i <= n; i++){for(int j = 1; j <= m; j++){//f[i][j] = 1;f[i][j] = 0;sum[i][j] = 0;}}for(int i = 1; i <= m; i++){cnt_low[i] = 0;}
}
void solve(){int n, i, j;cin >> n;for(i = 1; i <= n; i++){cin >> a[i];b[i] = a[i];}sort(b + 1, b + n + 1);int m = unique(b + 1, b + n + 1) - b - 1;init(n, m);for(i = 1; i <= n; i++){a[i] = lower_bound(b + 1, b + m + 1, a[i]) - b;cnt_low[a[i]]++;}for(i = 1; i <= m; i++){cnt_low[i] += cnt_low[i - 1];}// for(i = 1; i <= n; i++){// a[i] = lower_bound(b + 1, b + m + 1, a[i]) - b;// if(!cnt_low[a[i]]) cnt_low[a[i]] = a[i];不能这样写，因为b是去重过的，a[i]的排名不能代表小于等于a[i]的个数（小于真实值）// else cnt_low[a[i]]++; // }for(i = 1; i <= n; i++){for(j = 1; j <= m; j++){if(cnt_low[j] >= i){//小于等于j的数字要多于或等于i，f[i][j]才不为零if(i == 1) f[i][j] = 1;else f[i][j] = sum[i - 1][j] % mod;}sum[i][j] = (sum[i][j - 1] + f[i][j]) % mod;}cout << sum[i][m] << '\n';}
}
signed main(){ios::sync_with_stdio(0);cin.tie(0);int T;cin >> T;while(T--){solve();}return 0;
}
)
