| # | Time | Username | Problem | Language | Result | Execution time | Memory |
|---|---|---|---|---|---|---|---|
| 953659 | ifateen | Boarding Passes (BOI22_passes) | C++14 | 0 ms | 0 KiB |
This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
#define int long long
const int MAXN = 1e5 + 5, MAXG = 15;
map<char, int> m;
vector<vector<int>> pos;
int G;
long double dp[1 << MAXG], PREF[MAXG][MAXG][MAXN], SUF[MAXN][MAXN][MAXG];
long double compute(int i, int cnt, int mask) {
long double ret = 0;
int rcnt = pos[i].size() - cnt;
ret += cnt * (cnt - 1) * 0.25;
ret += rcnt * (rcnt - 1) * 0.25;
for (int j = 0; j < G; ++j) {
if (mask & (1 << j)) ret += (cnt ? PREF[i][j][cnt - 1] : 0) + (rcnt ? SUF[i][j][rcnt - 1] : 0);
}
return ret;
}
signed main() {
string s;
cin >> s;
vector<int> v(s.length());
int cnt = 0;
for (int i = 0; i < s.length(); ++i) {
if (m.find(s[i]) != m.end()) v[i] = m[s[i]];
else v[i] = m[s[i]] = cnt++;
}
G = *max_element(begin(v), end(v)) + 1;
pos.resize(G);
int n = s.length();
for (int i = 0; i < n; ++i) pos[v[i]].push_back(i);
dp[0] = 0;
for (int i = 0; i < G; ++i) {
for (int j = 0; j < G; ++j) {
if (i == j) continue;
int ptr = 0, cant = 0;
for (int k = 0; k < pos[i].size(); ++k) {
while (ptr < pos[i][k]) cant += v[ptr++] == j;
PREF[i][j][k] = cant;
if (k) PREF[i][j][k] += PREF[i][j][k - 1];
}
ptr = n - 1, cant = 0;
for (int k = 0; k < pos[i].size(); ++k) {
int idx = pos[i].size() - k - 1;
while (ptr > pos[i][idx]) cant += v[ptr--] == j;
SUF[i][j][k] = cant;
if (k) SUF[i][j][k] += SUF[i][j][k - 1];
}
}
}
for (int mask = 1; mask < (1 << G); mask++) {
dp[mask] = 1e18;
for (int i = 0; i < G; i++) {
if (!(mask & (1 << i))) continue;
long double EV = compute(i, pos[i].size(), mask);
int l = 0, r = pos[i].size() - 1;
while (l <= r) {
int mid = (l + r) >> 1;
if (compute(i, mid, mask) <= compute(i, mid + 1, mask)) EV = min(EV, compute(i, mid, mask)), r = mid - 1;
else l = mid + 1;
}
dp[mask] = min(dp[mask], EV + dp[mask ^ (1 << i)]);
}
}
cout << fixed << setprecision(8) << dp[(1 << G) - 1];
}