Submission #953660

#	Time	Username	Problem	Language	Result	Execution time	Memory
953660		ifateen	Boarding Passes (BOI22_passes)	C++17	100 / 100	265 ms	100292 KiB

passes

#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];
int PREF[MAXG][MAXG][MAXN], SUF[MAXG][MAXG][MAXN];
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];
}

Compilation message (stderr)

passes.cpp: In function 'int main()':
passes.cpp:25:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   25 |     for (int i = 0; i < s.length(); ++i) {
      |                     ~~^~~~~~~~~~~~
passes.cpp:38:31: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   38 |             for (int k = 0; k < pos[i].size(); ++k) {
      |                             ~~^~~~~~~~~~~~~~~
passes.cpp:44:31: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   44 |             for (int k = 0; k < pos[i].size(); ++k) {
      |                             ~~^~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 25 / 25
• Subtask 3: 30 / 30
• Subtask 4: 40 / 40