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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. #define endl '\n'
  4. #define int long long
  5. const int MOD = 1000000007;
  6. const int INF = LLONG_MAX/2;
  7. const int MAXN = 100000;
  8. int primes[1000000];
  9.  
  10. void seive(){
  11.     fill(primes, primes + 1000000, 1);
  12.     primes[0] = primes[1] = 0;
  13.     for(int i = 2 ; i*i < 1000000 ; i++){
  14.         if(primes[i]){
  15.             for(int j = i*i ; j < 1000000 ; j += i){
  16.                 primes[j] = 0;
  17.             }
  18.         }
  19.     }
  20. }
  21. bool isPrime(int n){
  22.     if(n <= 1) return false;
  23.     for(int i = 2 ; i*i <= n ; i++){
  24.         if(n % i == 0) return false;
  25.     }
  26.     return true;
  27. }
  28. int gcd(int a, int b){
  29.     if(a == 0) return b;
  30.     return gcd(b % a, a);
  31. }
  32. int power(int a, int b) {
  33.     int res = 1;
  34.     a %= MOD;
  35.     while (b > 0) {
  36.         if (b & 1) res = res * a % MOD;
  37.         a = a * a % MOD;
  38.         b >>= 1;
  39.     }
  40.     return res;
  41. }
  42.  
  43. // nCr % MOD for n < MOD
  44. int nCrModP(int n, int r) {
  45.     if (r > n) return 0;
  46.     if (r == 0 || r == n) return 1;
  47.  
  48.     int numerator = 1, denominator = 1;
  49.     for (int i = 0; i < r; i++) {
  50.         numerator = (numerator * (n - i)) % MOD;
  51.         denominator = (denominator * (i + 1)) % MOD;
  52.     }
  53.     return (numerator * power(denominator, MOD - 2)) % MOD;
  54. }
  55.  
  56. // Lucas's Theorem
  57. int lucas(int n, int r) {
  58.     if (r == 0) return 1;
  59.     return (lucas(n / MOD, r / MOD) * nCrModP(n % MOD, r % MOD)) % MOD;
  60. }
  61. void solve() {
  62.     int n,target;
  63.     cin>>n>>target;
  64.     int A[n];
  65.     for(int i = 0 ; i<n ; i++){
  66.         cin>>A[i];
  67.     }
  68.     if(target%2!=0){
  69.         cout<<0<<endl;
  70.     }
  71.     else{
  72.     int totalcnt = 0;
  73.     int c1 = 0,c2=0;
  74.     for(int i = 0 ; i<n ; i++){
  75.         if(A[i]>=0 && A[i]==(target/2)){
  76.             c1++;
  77.         }
  78.     }
  79.     for(int i = 0 ; i<n ; i++){
  80.         if(A[i]>=0 && A[i]<(target/2)){
  81.             c2++;
  82.         }
  83.     }
  84.     totalcnt += (c1*c2);
  85.     totalcnt += (c1*(c1-1))/2;
  86.     c1 = 0,c2=0;
  87.     for(int i = 0 ; i<n ; i++){
  88.         if(A[i]<0 && A[i]==(-(target/2))){
  89.             c1++;
  90.         }
  91.     }
  92.     for(int i = 0 ; i<n ; i++){
  93.         if(A[i]<0 && (A[i]>(-(target/2)))){
  94.             c2++;
  95.         }
  96.     }
  97.     totalcnt += (c1*c2);
  98.     totalcnt += (c1*(c1-1))/2;
  99.     c1 = 0 ,c2 =0;
  100.     for(int i = 0 ; i<n ; i++){
  101.         if(A[i]>=0 && A[i]==(target/2)){
  102.             c1++;
  103.         }
  104.     }
  105.     for(int i = 0 ; i<n ; i++){
  106.         if(A[i]<0 && abs(A[i])<=(target/2)){
  107.             c2++;
  108.         }
  109.     }
  110.     totalcnt += (c1*c2);
  111.     c1 = 0,c2=0;
  112.     for(int i = 0 ; i<n ; i++){
  113.         if(A[i]<0 && A[i]==(-(target/2))){
  114.             c1++;
  115.         }
  116.     }
  117.     for(int i = 0 ; i<n ; i++){
  118.         if(A[i]>=0 && abs(A[i])<(target/2)){
  119.             c2++;
  120.         }
  121.     }
  122.     totalcnt += (c1*c2);
  123.     cout<<totalcnt<<endl;
  124.     }
  125. } 
  126. signed main(){
  127.     ios::sync_with_stdio(false); cin.tie(NULL);
  128.     //int t;
  129.     //cin >> t;
  130.     //while(t--){
  131.         solve();
  132.     //}
  133.     return 0;
  134. }
Success #stdin #stdout 0.01s 5316KB
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https://ideone.com/OP8F5n
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

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