#include<bits/stdc++.h>
using namespace std;
//#pragma GCC optimize("O3,unroll-loops")
//#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#define rep(i, x, y) for(int i = x; i <= y; ++i)
#define repi(i,x,y) for(int i = x; i >= y; --i)
#define ci(x) int x; cin>> x
#define TC(t) ci(t); while(t--)
#define fi first
#define se second
#define pb push_back
#define all(x) x.begin(), x.end()
#define cii(x, y) ci(x); ci(y)
#define ciii(x, y, z) ci(x); ci(y); ci(z)
#define mp make_pair
//#define int long long
typedef long long ll;
typedef vector<int> vi;
const int N = 1e3 + 5;
const int NN = 16 + 15;
const int mod = 1e9+7;
const int mod1 = 1e9 + 9;
const int pi = 31;
const ll inf = 1e15 + 6;
const int block = 500;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, -1, 0, 1};
void readfile(){
#ifdef ONLINE_JUDGE
#else
freopen("text.inp", "r", stdin);
#endif // ONLINE_JUDGE
// freopen("text.inp", "r", stdin);
// freopen("template.out", "w", stdout);
}
int n, L;
int a[N];
void inp(){
cin >> n >> L;
for(int i = 1; i <= n; ++i) cin >> a[i];
sort(a + 1, a + n + 1);
}
int add(int x, int y){
x += y;
while(x < 0) x += mod;
while(x >= mod) x -= mod;
return x;
}
int mul(int x, int y){
return (x * 1LL * y) % mod;
}
int f[N][N][N][3];
void process(){
f[1][1][0][0] = 1;
f[1][1][0][1] = 2;
f[1][1][0][2] = 1;
// apply open close interval trick,
// each component increase by (2 * j - t) *(a[i + 1] - a[i])
// so that for a[i + 2] - a[i + 1] can combine with a[i + 1] - a[i] at some endpoint
// since we have at most 2*j place to put but minus the fixed point
for(int i = 1; i < n; ++i){
int diff = a[i + 1] - a[i];
for(int j = 1; j <= i; ++j){
for(int sum = 0; sum <= L; ++sum){
for(int t = 0; t <= 2; ++t){
int val = sum + (2*j - t) * (a[i + 1] - a[i]);
if(val > L) continue;
if(j >= 2) // merge 2 cc
f[i + 1][j - 1][val][t] = add(f[i + 1][j - 1][val][t], mul(f[i][j][sum][t], j - 1));
if(t==0){
// new cc
if(sum + (j + 1) * diff)
f[i + 1][j + 1][val][0] = add(f[i + 1][j + 1][val][0], mul(f[i][j][sum][t], j + 1));
// new cc but in one endpoint
f[i + 1][j + 1][val][1] = add(f[i + 1][j + 1][val][1], mul(f[i][j][sum][t], 2)); // two endpoint
// attach to a cc
f[i + 1][j][val][0] = add(f[i + 1][j][val][0], mul(f[i][j][sum][t], 2*j));
// attach to a cc but at one endpoint
f[i + 1][j][val][1] = add(f[i + 1][j][val][1], mul(f[i][j][sum][t], 2));
}
else if(t==1){
// new cc
f[i + 1][j + 1][val][1] = add(f[i + 1][j + 1][val][1], mul(f[i][j][sum][t], j));
// new cc but in one endpoint
f[i + 1][j + 1][val][2] = add(f[i + 1][j + 1][val][2], mul(f[i][j][sum][t], 1));
// attach to a cc
f[i + 1][j][val][1] = add(f[i + 1][j][val][1], mul(f[i][j][sum][t], 2*j - 1));
// attach to a cc but at one endpoint
f[i + 1][j][val][2] = add(f[i + 1][j][val][2], mul(f[i][j][sum][t], 1));
}
else{
if(j >= 2){
// new cc
f[i + 1][j + 1][val][2] = add(f[i + 1][j + 1][val][2], mul(f[i][j][sum][t], j - 1));
// attach to a cc
f[i + 1][j][val][2] = add(f[i + 1][j][val][2], mul(f[i][j][sum][t], 2*j - 2));
}
}
}
}
}
}
int res = 0;
for(int i = 0; i <= L; ++i)
res = add(res, f[n][1][i][2]);
cout << res;
}
int main() {
// readfile();
ios_base::sync_with_stdio(0);
cin.tie(0);
inp();
process();
return 0;
}
Compilation message
skyscraper.cpp: In function 'void readfile()':
skyscraper.cpp:33:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
33 | freopen("text.inp", "r", stdin);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
/usr/bin/ld: failed to convert GOTPCREL relocation; relink with --no-relax
collect2: error: ld returned 1 exit status
