Buggy python submission (verdict: Time Limit Exceeded):
#----------------------------------------------------------
P = 10**9 + 7
N = 100001 #使う最大値+1以上にする、値に注意3*10^5とかにしとくと安心
inv = [0] + [1] # 1/x
finv = [1] + [1] # 1/x!
fac = [1] + [1] # x!
for i in range(2,N):
  inv += [inv[P % i] * (P - int(P / i)) % P]
  fac += [(fac[i-1] * i) % P]
  finv += [(finv[i-1] * inv[i]) % P]

def comb(a, b):
    if a<b or a<0 or b<0:
        return 0 # error
    return (fac[a] * ((finv[b] * finv[a-b]) % P)) %P
#----------------------------------------------------------

n=int(input())
x=list(map(int,input().split()))
ans=0
for i in range(n-1):
    t = (x[n-1]-x[i])%P
    o =(fac[i]*fac[n-2-i])%P
    g = (comb(n-1,n-1-i)*o)%P
    t = (t * g)%P
    ans=(ans+t)%P

for i in range(n-1):
    for j in range(i+1,n-1):
        t = (x[j]-x[i])%P
        o =(fac[n-1-j+i-1]*fac[j-i-1])%P
        g = (comb(n-1,j-i+1)*o)%P
        t = (t * g)%P
        ans=(ans + t)%P
print(ans%P)


Fixed submission:
#----------------------------------------------------------
P = 10**9 + 7
N = 100001 #使う最大値+1以上にする、値に注意3*10^5とかにしとくと安心
inv = [0] + [1] # 1/x
finv = [1] + [1] # 1/x!
fac = [1] + [1] # x!
for i in range(2,N):
  inv += [inv[P % i] * (P - int(P / i)) % P]
  fac += [(fac[i-1] * i) % P]
  finv += [(finv[i-1] * inv[i]) % P]

def comb(a, b):
    if a<b or a<0 or b<0:
        return 0 # error
    return (fac[a] * ((finv[b] * finv[a-b]) % P)) %P
#----------------------------------------------------------

n=int(input())
x=list(map(int,input().split()))
s = [0] * n
for i in range(n):
    s[i] = x[i] + (s[i-1] if i>0 else 0)
ans=0

for i in range(n-1):
    t = (x[n-1]-x[n-2-i])%P
    t = (t * (fac[n-1]*inv[i+1])%P)%P
    ans=(ans+t)%P
for i in range(1, n-1):
    t = (s[n-2] - s[i-1] - s[n-2-i])%P
    p = (((fac[n-1] * inv[i])%P) * inv[i+1])%P
    ans = (ans + (t*p)%P)%P

print(ans%P)

Buggy python submission (verdict: Time Limit Exceeded):
def cmb(n, r, mod):
    if ( r<0 or r>n ):
        return 0
    r = min(r, n-r)
    return g1[n] * g2[r] * g2[n-r] % mod
  
import sys
sys.setrecursionlimit(100000)
from math import factorial


mod = 10**9+7 #出力の制限
N = 10**5+1
g1 = [1, 1] # 元テーブル
g2 = [1, 1] #逆元テーブル
inverse = [0, 1] #逆元テーブル計算用テーブル
f=[0]*N
f[0]=1
for i in range(1,N):
  f[i]=(f[i-1]*i)%mod

for i in range( 2, N + 1 ):
    g1.append( ( g1[-1] * i ) % mod )
    inverse.append( ( -inverse[mod % i] * (mod//i) ) % mod )
    g2.append( (g2[-1] * inverse[-1]) % mod )

n=int(input())
x=list(map(int,input().split()))
ans=0
for i in range(n-1):
  for j in range(i+1,n):
    if j!=n-1:
      t = (x[j]-x[i])%mod
      o =( f[n-1-j+i-1]*f[j-i-1])%mod
      g = (cmb(n-1,j-i+1,mod)*o)%mod
      t = (t * g)%mod

      ans=(ans + t)%mod
    else:
      t = (x[j]-x[i])%mod
      o =( f[n-1-j+i]*f[j-i-1])%mod
      g = (cmb(n-1,j-i,mod)*o)%mod
      t = (t * g)%mod
      ans=(ans+t)%mod
print(ans%mod)


Fixed submission:
#----------------------------------------------------------
P = 10**9 + 7
N = 100001 #使う最大値+1以上にする、値に注意3*10^5とかにしとくと安心
inv = [0] + [1] # 1/x
finv = [1] + [1] # 1/x!
fac = [1] + [1] # x!
for i in range(2,N):
  inv += [inv[P % i] * (P - int(P / i)) % P]
  fac += [(fac[i-1] * i) % P]
  finv += [(finv[i-1] * inv[i]) % P]

def comb(a, b):
    if a<b or a<0 or b<0:
        return 0 # error
    return (fac[a] * ((finv[b] * finv[a-b]) % P)) %P
#----------------------------------------------------------

n=int(input())
x=list(map(int,input().split()))
s = [0] * n
for i in range(n):
    s[i] = x[i] + (s[i-1] if i>0 else 0)
ans=0

for i in range(n-1):
    t = (x[n-1]-x[n-2-i])%P
    t = (t * (fac[n-1]*inv[i+1])%P)%P
    ans=(ans+t)%P
for i in range(1, n-1):
    t = (s[n-2] - s[i-1] - s[n-2-i])%P
    p = (((fac[n-1] * inv[i])%P) * inv[i+1])%P
    ans = (ans + (t*p)%P)%P

print(ans%P)

Buggy python submission (verdict: Time Limit Exceeded):
def cmb(n, r, mod):
    if ( r<0 or r>n ):
        return 0
    r = min(r, n-r)
    return g1[n] * g2[r] * g2[n-r] % mod
  
import sys
sys.setrecursionlimit(100000)
from math import factorial


mod = 10**9+7 #出力の制限
N = 10**5+1
g1 = [1, 1] # 元テーブル
g2 = [1, 1] #逆元テーブル
inverse = [0, 1] #逆元テーブル計算用テーブル
f=[0]*N
f[0]=1
for i in range(1,N):
  f[i]=(f[i-1]*i)%mod

for i in range( 2, N + 1 ):
    g1.append( ( g1[-1] * i ) % mod )
    inverse.append( ( -inverse[mod % i] * (mod//i) ) % mod )
    g2.append( (g2[-1] * inverse[-1]) % mod )

n=int(input())
x=list(map(int,input().split()))
ans=0
for i in range(n-1):
  for j in range(i+1,n):
    if j!=n-1:
      ans=(ans+(((x[j]-x[i]))*cmb(n-1,j-i+1,mod)*f[n-1-j+i-1]*f[j-i-1])%mod)%mod
    else:
      ans=(ans+(((x[j]-x[i]))*cmb(n-1,j-i,mod)*f[n-1-j+i]*f[j-i-1])%mod)%mod
print(ans%mod)


Fixed submission:
#----------------------------------------------------------
P = 10**9 + 7
N = 100001 #使う最大値+1以上にする、値に注意3*10^5とかにしとくと安心
inv = [0] + [1] # 1/x
finv = [1] + [1] # 1/x!
fac = [1] + [1] # x!
for i in range(2,N):
  inv += [inv[P % i] * (P - int(P / i)) % P]
  fac += [(fac[i-1] * i) % P]
  finv += [(finv[i-1] * inv[i]) % P]

def comb(a, b):
    if a<b or a<0 or b<0:
        return 0 # error
    return (fac[a] * ((finv[b] * finv[a-b]) % P)) %P
#----------------------------------------------------------

n=int(input())
x=list(map(int,input().split()))
s = [0] * n
for i in range(n):
    s[i] = x[i] + (s[i-1] if i>0 else 0)
ans=0

for i in range(n-1):
    t = (x[n-1]-x[n-2-i])%P
    t = (t * (fac[n-1]*inv[i+1])%P)%P
    ans=(ans+t)%P
for i in range(1, n-1):
    t = (s[n-2] - s[i-1] - s[n-2-i])%P
    p = (((fac[n-1] * inv[i])%P) * inv[i+1])%P
    ans = (ans + (t*p)%P)%P

print(ans%P)

Buggy python submission (verdict: Time Limit Exceeded):
def cmb(n, r, mod):
    if ( r<0 or r>n ):
        return 0
    r = min(r, n-r)
    return g1[n] * g2[r] * g2[n-r] % mod
  
import sys
sys.setrecursionlimit(100000)
from math import factorial


mod = 10**9+7 #出力の制限
N = 10**5+1
g1 = [1, 1] # 元テーブル
g2 = [1, 1] #逆元テーブル
inverse = [0, 1] #逆元テーブル計算用テーブル
f=[0]*N
f[0]=1
for i in range(1,N):
  f[i]=(f[i-1]*i)%mod

for i in range( 2, N + 1 ):
    g1.append( ( g1[-1] * i ) % mod )
    inverse.append( ( -inverse[mod % i] * (mod//i) ) % mod )
    g2.append( (g2[-1] * inverse[-1]) % mod )

n=int(input())
x=list(map(int,input().split()))
ans=0
for i in range(n-1):
  for j in range(i+1,n):
    if j!=n-1:
      ans+=(((x[j]-x[i]))*cmb(n-1,j-i+1,mod)*f[n-1-j+i-1]*f[j-i-1]%mod)
    else:
      ans+=(((x[j]-x[i]))*cmb(n-1,j-i,mod)*f[n-1-j+i]*f[j-i-1]%mod)
print(ans%mod)


Fixed submission:
#----------------------------------------------------------
P = 10**9 + 7
N = 100001 #使う最大値+1以上にする、値に注意3*10^5とかにしとくと安心
inv = [0] + [1] # 1/x
finv = [1] + [1] # 1/x!
fac = [1] + [1] # x!
for i in range(2,N):
  inv += [inv[P % i] * (P - int(P / i)) % P]
  fac += [(fac[i-1] * i) % P]
  finv += [(finv[i-1] * inv[i]) % P]

def comb(a, b):
    if a<b or a<0 or b<0:
        return 0 # error
    return (fac[a] * ((finv[b] * finv[a-b]) % P)) %P
#----------------------------------------------------------

n=int(input())
x=list(map(int,input().split()))
s = [0] * n
for i in range(n):
    s[i] = x[i] + (s[i-1] if i>0 else 0)
ans=0

for i in range(n-1):
    t = (x[n-1]-x[n-2-i])%P
    t = (t * (fac[n-1]*inv[i+1])%P)%P
    ans=(ans+t)%P
for i in range(1, n-1):
    t = (s[n-2] - s[i-1] - s[n-2-i])%P
    p = (((fac[n-1] * inv[i])%P) * inv[i+1])%P
    ans = (ans + (t*p)%P)%P

print(ans%P)