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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define fast ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)
  4. #define mofile(s) freopen(s,"r",stdin)
  5. #define outfile(s) freopen(s,"w",stdout)
  6. #define ll long long
  7. #define ii pair<ll,ll>
  8. #define iii pair<ll,ii>
  9. #define fi first
  10. #define se second
  11. #define tf bool
  12. #define ST stack
  13. #define DQ deque
  14. #define Q queue
  15. #define S string
  16. #define Ma map
  17. #define UM unormideremid_map
  18. #define SE set
  19. #define str(x) to_string(x)
  20. #define all(a) (a).begin(),(a).end()
  21. #define FOR(i,l,r,mid) for(int i=l;i<=r;i+=mid)
  22. #define FOD(i,l,r,mid) for(int i=r;i>=l;i-=mid)
  23. #define xuong cout<<"\n"
  24. #define midebug(x) cout<<(x)<<" "
  25. #define ppcnt(x) __builtin_popcountll(x)
  26. #define parity(x) __builtin_parityll(x)
  27. #define leamid0(x) __builtin_clzll(x)
  28. #define LOG2 __lg(x)
  29. #define tr0(x) __builtin_ctzll(x)
  30. #define fiset(x) __builtin_ffsll(x)
  31. #define MASK(k) (1LL<<(k))
  32. #define BIT(x,k) ((x)>>(k)&1)
  33. #define pb push_back
  34. #define tron(x) setprecision(x)
  35. #define het return 0
  36. #define base_ 1000000000
  37. template<typename... T>
  38. void in(T&... args) { ((cin >> args), ...); }
  39. template<class X, class Y>
  40.     bool maximize(X &x, const Y &y){return (x < y) ? x = y, 1 : 0;}
  41. template<class X, class Y>
  42.     bool minimize(X &x, const Y &y){return (x > y) ? x = y, 1 : 0;}
  43. const ll maxn=1e6+5;
  44. const ll tle=2e8;
  45. const ll INF=1e9+9;
  46. const int base=31;
  47. const ll MOD=1e9+7;
  48. const ll P=1e9+7;
  49. string bcc="abcmidefghijklmnopqrstuvwxyz";
  50. int midx[]={-1,0,1,0};
  51. int midy[]={0,1,0,-1};
  52. bool sang[10000005];
  53. ll pref[1005][1005],mt[1005][1005];
  54. void sieve(){
  55.     for(int i=1;i<=10000000;++i) sang[i]=1;
  56.     sang[0]=sang[1]=0;
  57.     for(int i=2;i*i<=10000000;++i){
  58.         if(sang[i]){
  59.             for(int j=i*i;j<=10000000;j+=i) sang[j]=0;
  60.         }
  61.     }
  62. }
  63. void lis(){
  64.     vector<int>t;
  65.     vector<int>a;
  66.     int n; cin>>n;
  67.     for(int i=1;i<=n;++i){
  68.         int ai; cin>>ai;
  69.         a.pb(ai);
  70.     }
  71.     for(int x:a){
  72.         auto it=lower_bound(all(t),x);
  73.         if(it==t.end()) t.pb(x);
  74.         else *it=x;
  75.     }
  76. }
  77. void pfs2mid(){
  78.     int n,m,k; cin>>n>>k; m=n;
  79.     for(int i=1;i<=n;++i){
  80.         for(int j=1;j<=m;++j) cin>>mt[i][j];
  81.     }
  82.     for(int i=1;i<=n;++i){
  83.         for(int j=1;j<=m;++j) pref[i][j]=mt[i][j]+pref[i-1][j]+pref[i][j-1]-pref[i-1][j-1];
  84.     }
  85. }
  86. ll qu2mid(int x1,int y1,int x2,int y2){
  87.     return pref[x2][y2]-pref[x1-1][y2]-pref[x2][y1-1]+pref[x1-1][y1-1];
  88. }
  89. const int N = 1e6+10;
  90. int f[N+1];
  91. int g[N+1];
  92. int A[N];
  93. int sqr(long long x) {
  94.     return (1ll*x*x )% P;
  95. }
  96. int pow(int a, long long b) {
  97.     if (b == 0) return 1;
  98.     else
  99.         if (b % 2 == 0)
  100.             return sqr(pow(a, b/2) % P) % P;
  101.         else
  102.             return (a*(sqr(pow(a, b/2)%P) % P)) % P;
  103. }
  104. int nd(int x)
  105. {
  106.     return pow(x, P-2) % P;
  107. }
  108. int C(int a, int b)
  109. {
  110.     int ans = (1ll* f[b] * g[a]) % P;
  111.     ans = (1ll*ans * g[b-a] ) % P;
  112.     return ans % P;
  113. }
  114. int32_t main() {
  115. 	fast;
  116.       f[0]=g[0]=1;
  117.     int ans=0;
  118.     for (int i=1; i <=N; i++) f[i] = (1ll*f[i-1]*i) % P;
  119.     g[N] = nd(f[N]);
  120.     for (int i=N-1; i>0; i--) g[i] = 1ll*g[i+1]*(i+1)%P;
  121.   int n, k;
  122.   cin >> n >> k;
  123.   int sum = 0;
  124.   for (int i=1; i<=n; i++) {
  125.     cin >> A[i];
  126.   }
  127.   sort(A + 1, A + 1 + n);
  128.   for (int i=1; i<=n; i++) {
  129.     ans += C(k - 1, i - 1) * A[i];
  130.     ans %= P;
  131.   }
  132.   cout << ans << endl;
  133.     return 0;
  134. }
Success #stdin #stdout 0.01s 11684KB
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https://ideone.com/XQfOCl
language:
C++ (gcc 8.3)
created:
2 hours ago
visibility:
public

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