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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 Q 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<class X, class Y>
  38.     bool maximize(X &x, const Y &y){return (x < y) ? x = y, 1 : 0;}
  39. template<class X, class Y>
  40.     bool minimize(X &x, const Y &y){return (x > y) ? x = y, 1 : 0;}
  41. const int maxn=1e6+5;
  42. const ll tle=2e8;
  43. const ll INF=1e9+9;
  44. const int base=31;
  45. string bcc="abcmidefghijklmnopqrstuvwxyz";
  46. int midx[]={-1,0,1,0};
  47. int midy[]={0,1,0,-1};
  48. bool sang[10000005];
  49. ll pref[1005][1005],mt[1005][1005];
  50. void sieve(){
  51.     for(int i=1;i<=10000000;++i) sang[i]=1;
  52.     sang[0]=sang[1]=0;
  53.     for(int i=2;i*i<=10000000;++i){
  54.         if(sang[i]){
  55.             for(int j=i*i;j<=10000000;j+=i) sang[j]=0;
  56.         }
  57.     }
  58. }
  59. void lis(){
  60.     vector<int>t;
  61.     vector<int>a;
  62.     int n; cin>>n;
  63.     for(int i=1;i<=n;++i){
  64.         int ai; cin>>ai;
  65.         a.pb(ai);
  66.     }
  67.     for(int x:a){
  68.         auto it=lower_bound(all(t),x);
  69.         if(it==t.end()) t.pb(x);
  70.         else *it=x;
  71.     }
  72. }
  73. void pfs2mid(){
  74.     int n,m,k; cin>>n>>k; m=n;
  75.     for(int i=1;i<=n;++i){
  76.         for(int j=1;j<=m;++j) cin>>mt[i][j];
  77.     }
  78.     for(int i=1;i<=n;++i){
  79.         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];
  80.     }
  81. }
  82. ll qu2mid(int x1,int y1,int x2,int y2){
  83.     return pref[x2][y2]-pref[x1-1][y2]-pref[x2][y1-1]+pref[x1-1][y1-1];
  84. }
  85. void open(){
  86.     if(fopen("mideptrai.INP","r")){
  87.         mofile("mideptrai.INP");
  88.         outfile("mideptrai.OUT");
  89.     }
  90. }
  91. ll a[maxn];
  92. int main(){
  93.     fast;
  94.     int n; cin>>n;
  95.     for(int i=0;i<n;++i) cin>>a[i];
  96.     sort(a,a+n);
  97.     ll c=0;
  98.     for(int k=2;k<n;k++){
  99.         int i=0,j=k-1;
  100.         while(i<j){
  101.             if(a[i]+a[j]>a[k]){
  102.                 c+=j-i;
  103.                 --j;
  104.             }else ++i;
  105.         }
  106.     }
  107.     cout<<c<<"\n";
  108.     het;
  109. }
Success #stdin #stdout 0s 5316KB
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https://ideone.com/45qyEY
language:
C++ (gcc 8.3)
created:
1 day ago
visibility:
public

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