We use cookies to ensure you have the best browsing experience on our website. Please read our cookie policy for more information about how we use cookies.
define FOR(i, a, b) for (int i = (a); i < (b); i++)
define REP(i, n) for (int i = 0; i < (n); i++)
int ripset()
{
int x;
cin>>x;
return x;
}
const int N = 3000;
int a[N];
int main()
{
int n = ripset();
long ans = 0;
REP(i, n)
a[i] = ripset();
sort(a, a+n);
unordered_map cnt;
for (int ii, i = 0; i < n; i = ii) {
for (ii = i+1; ii < n && a[i] == a[ii]; ii++);
if (ii-i > 1) {
int j = 0, k = i-1;
long s = 0, h = (ii-i)(ii-i-1)/2;
while (j < k)
if (a[j]+a[k] < a[i])
j++;
else if (a[j]+a[k] > a[i])
k--;
else if (a[j] == a[k]) {
int t = k-j+1;
ans += h(t-1)*t/2*s;
ans += h*t*(t-1)(t-2)(t-3)/24;
break;
} else {
int jj = j, kk = k;
for (; a[j] == a[jj]; jj++);
for (; a[k] == a[kk]; kk--);
int f = jj-j, g = k-kk;
ans += h*f*g*s;
ans += h*f*(f-1)g(g-1)/4;
s += f*g;
j = jj;
k = kk;
}
}
for (int jj, j = ii; j < n; j = jj) {
for (jj = j+1; jj < n && a[j] == a[jj]; jj++);
if (jj-j > 2) {
long h = long(jj-j)(jj-j-1)(jj-j-2)/6;
if (3*a[i] == a[j])
ans += long(ii-i)(ii-i-1)(ii-i-2)/6*h;
else {
int t = a[j]-2*a[i];
auto eq = equal_range(a, a+i, t);
if (eq.first != eq.second)
ans += long(eq.second-eq.first)(ii-i)(ii-i-1)/2*h;
auto it = cnt.find(a[j]-a[i]);
if (it != cnt.end())
ans += long(it->second)*(ii-i)h;
}
}
}
for (int jj, j = 0; j < i; j = jj) {
for (jj = j+1; jj < i && a[j] == a[jj]; jj++);
cnt[a[j]+a[i]] += (ii-i)(jj-j);
}
cnt[2*a[i]] += (ii-i)*(ii-i-1)/2;
}
cout<
include
using namespace std;
define FOR(i, a, b) for (int i = (a); i < (b); i++)
define REP(i, n) for (int i = 0; i < (n); i++)
int ripset() { int x; cin>>x; return x; }
const int N = 3000; int a[N];
int main() { int n = ripset(); long ans = 0; REP(i, n) a[i] = ripset(); sort(a, a+n); unordered_map cnt; for (int ii, i = 0; i < n; i = ii) { for (ii = i+1; ii < n && a[i] == a[ii]; ii++); if (ii-i > 1) { int j = 0, k = i-1; long s = 0, h = (ii-i)(ii-i-1)/2; while (j < k) if (a[j]+a[k] < a[i]) j++; else if (a[j]+a[k] > a[i]) k--; else if (a[j] == a[k]) { int t = k-j+1; ans += h(t-1)*t/2*s; ans += h*t*(t-1)(t-2)(t-3)/24; break; } else { int jj = j, kk = k; for (; a[j] == a[jj]; jj++); for (; a[k] == a[kk]; kk--); int f = jj-j, g = k-kk; ans += h*f*g*s; ans += h*f*(f-1)g(g-1)/4; s += f*g; j = jj; k = kk; } } for (int jj, j = ii; j < n; j = jj) { for (jj = j+1; jj < n && a[j] == a[jj]; jj++); if (jj-j > 2) { long h = long(jj-j)(jj-j-1)(jj-j-2)/6; if (3*a[i] == a[j]) ans += long(ii-i)(ii-i-1)(ii-i-2)/6*h; else { int t = a[j]-2*a[i]; auto eq = equal_range(a, a+i, t); if (eq.first != eq.second) ans += long(eq.second-eq.first)(ii-i)(ii-i-1)/2*h; auto it = cnt.find(a[j]-a[i]); if (it != cnt.end()) ans += long(it->second)*(ii-i)h; } } } for (int jj, j = 0; j < i; j = jj) { for (jj = j+1; jj < i && a[j] == a[jj]; jj++); cnt[a[j]+a[i]] += (ii-i)(jj-j); } cnt[2*a[i]] += (ii-i)*(ii-i-1)/2; } cout<
Can anyone please explain how the sqaure is formed in the first test case? Thanks
what we have to do in case of multiple possibility of square.....