Submission #574141

#	Time	Username	Problem	Language	Result	Execution time	Memory
574141		eecs	Boarding Passes (BOI22_passes)	C++17	30 / 100	2061 ms	1172 KiB

passes

#include <bits/stdc++.h>
using namespace std;
 
string str;
long long f[1 << 15];
vector<int> pos[15];
 
int main() {
    ios::sync_with_stdio(0), cin.tie(0);
    cin >> str;
    int n = *max_element(str.begin(), str.end()) - 'A' + 1;
    for (int i = 0; i < str.size(); i++) {
        pos[str[i] - 'A'].push_back(i);
    }
    fill(f + 1, f + (1 << n), 1e18);
    for (int S = 0; S < 1 << n; S++) {
        for (int i = 0; i < n; i++) if (!(S >> i & 1)) {
            if (pos[i].empty()) { f[S | (1 << i)] = f[S]; continue; }
            auto calc = [&](int p) {
                int c0 = 0, c1 = 0;
                long long s = 0;
                for (int j = p; ~j; j--) {
                    if (str[j] - 'A' == i) c0++;
                    else if (S >> (str[j] - 'A') & 1) s += c0;
                }
                for (int j = p + 1; j < str.size(); j++) {
                    if (str[j] - 'A' == i) c1++;
                    else if (S >> (str[j] - 'A') & 1) s += c1;
                }
                return 2 * s + 1LL * c0 * (c0 - 1) / 2 + 1LL * c1 * (c1 - 1) / 2;
            };
            f[S | (1 << i)] = min(f[S | (1 << i)], f[S] + calc(-1));
            int l = 1, r = pos[i].size() - 1, p = 0;
            while (l <= r) {
                int mid = (l + r) / 2;
                calc(pos[i][mid]) < calc(pos[i][mid - 1]) ? l = (p = mid) + 1 : r = mid - 1;
            }
            f[S | (1 << i)] = min(f[S | (1 << i)], f[S] + calc(pos[i][p]));
        }
    }
    cout << f[(1 << n) - 1] / 2 << (f[(1 << n) - 1] % 2 ? ".5" : "") << "\n";
    return 0;
}

Compilation message (stderr)

passes.cpp: In function 'int main()':
passes.cpp:12:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   12 |     for (int i = 0; i < str.size(); i++) {
      |                     ~~^~~~~~~~~~~~
passes.cpp: In lambda function:
passes.cpp:26:39: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   26 |                 for (int j = p + 1; j < str.size(); j++) {
      |                                     ~~^~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 25 / 25
• Subtask 3: 0 / 30
• Subtask 4: 0 / 40