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QOJ
ID | Problem | Submitter | Result | Time | Memory | Language | File size | Submit time | Judge time |
---|---|---|---|---|---|---|---|---|---|
#390885 | #4770. Binomial coefficients | I_Love_Sonechka# | AC ✓ | 36ms | 202872kb | C++17 | 2.1kb | 2024-04-16 01:38:07 | 2024-04-16 01:38:07 |
Judging History
answer
#include <bits/stdc++.h>
#include <math.h>
using namespace std;
// c++ short types
#define Int long long
#define vt vector
const Int inf = 1e17+1;
const int nmax = 5000;
Int dp[nmax][nmax];
map<Int, vt<array<Int, 2>>> vals;
void precalc() {
memset(dp, 0, sizeof(dp));
for(int n = 0; n < nmax; ++n) {
for(int k = 0; k <= n; ++k) {
if(k == 0){
dp[n][k] = 1;
} else {
dp[n][k] = dp[n-1][k] + dp[n-1][k-1];
}
dp[n][k] = min(dp[n][k], inf);
if(dp[n][k] < inf && k != 0 && k != n) {
vals[dp[n][k]].push_back({n, k});
}
}
}
}
void solver() {
Int m; cin >> m;
set<array<Int, 2>> pairs;
auto cnk = [&](Int n, Int k) -> Int {
if(n <= k) {
return 0;
}
if(n < nmax) {
return dp[n][k];
}
if(k > n - k) {
k = n-k;
}
__int128 fact = 1;
for(__int128 i = 1; i <= k; ++i) {
fact *= i;
}
__int128 value = 1;
for(__int128 i = 0; i < k; ++i) {
value *= (n-i);
if(value / fact > inf) {
return inf;
}
}
return value / fact;
};
for(Int k = 1; k <= min(10ll, m); ++k) {
Int fact = 1;
for(int i = 1; i <= k; ++i) {
fact *= 1;
}
auto f = [&](Int n) -> Int {
if(n <= k) {
return 0ll;
}
__int128 value = 1;
for(__int128 i = 0; i < k; ++i) {
// value * (n-i) / fact > inf
// value / fact * (n-i) > inf
value *= (n-i);
if(value / fact > inf) {
return inf;
}
}
return value / fact;
};
Int l = 0, r = m + 1;
assert(f(r) > m and f(l) <= m);
while(r - l > 1) {
Int med = (l+r)>>1;
if(cnk(med, k) <= m) {
l = med;
} else {
r = med;
}
}
if(cnk(l, k) == m) {
pairs.insert({l, k});
pairs.insert({l, l-k});
}
}
for(auto p : vals[m]) {
pairs.insert(p);
}
cout << pairs.size() << "\n";
for(auto [a, b] : pairs) {
cout << "(" << a << "," << b << ") ";
assert(cnk(a, b) == m);
}
cout << "\n";
}
int main()
{
precalc();
ios::sync_with_stdio(false); cin.tie(nullptr);
int tt = 1;
cin >> tt;
for(int t = 0; t < tt; ++t) {
solver();
}
return 0;
}
Details
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Test #1:
score: 100
Accepted
time: 36ms
memory: 202600kb
input:
2 2 15
output:
1 (2,1) 4 (6,2) (6,4) (15,1) (15,14)
result:
ok 4 lines
Test #2:
score: 0
Accepted
time: 32ms
memory: 202872kb
input:
100 2 3 4 5 6 7 8 9 10 15 120 3003 24310 495918532948104 1000000000000000 210 1540 2701 7140 11628 48620 614386 705432 817190 885115 4200651 4610166 5311735 5918520 6299475 6666891 6876486 7023974 7610851 8002000 8948565 9016381 9411291 9695406 30421755 1676056044 9075135300 101766230790 13784652882...
output:
1 (2,1) 2 (3,1) (3,2) 2 (4,1) (4,3) 2 (5,1) (5,4) 3 (4,2) (6,1) (6,5) 2 (7,1) (7,6) 2 (8,1) (8,7) 2 (9,1) (9,8) 4 (5,2) (5,3) (10,1) (10,9) 4 (6,2) (6,4) (15,1) (15,14) 6 (10,3) (10,7) (16,2) (16,14) (120,1) (120,119) 8 (14,6) (14,8) (15,5) (15,10) (78,2) (78,76) (3003,1) (3003,3002) 6 (...
result:
ok 200 lines