Submission #906485

#	Time	Username	Problem	Language	Result	Execution time	Memory
906485		LucaIlie	Chorus (JOI23_chorus)	C++17	61 / 100	7103 ms	13136 KiB

chorus

#include <bits/stdc++.h>

using namespace std;

const int MAX_N = 1e6;
const long long INF = 1e18;
int a[MAX_N + 1], countLowerA[MAX_N + 1], minGroups[MAX_N + 1], maxGroups[MAX_N + 1];
long long sumA[MAX_N + 1], sumLowerA[MAX_N + 1], minSwaps[MAX_N + 1];

void computeDP( int n, long long cost ) {
    for ( int i = 1; i <= n; i++ ) {
        minSwaps[i] = INF;
        minGroups[i] = n + 1;
        maxGroups[i] = 0;
        for ( int j = i - 1; j >= 0; j-- ) {
            long long s = (minSwaps[j] + sumA[j]) + i * (-j);
            if ( s < minSwaps[i] ) {
                minSwaps[i] = s;
                minGroups[i] = minGroups[j] + 1;
                maxGroups[i] = maxGroups[j] + 1;
            } else if ( s == minSwaps[i] ) {
                minGroups[i] = min( minGroups[i], minGroups[j] + 1 );
                maxGroups[i] = max( maxGroups[i], maxGroups[j] + 1 );
            }
        }
        minSwaps[i] += i * countLowerA[i] - sumLowerA[i] + cost;
    }
}

int main() {
    int n, k, swaps;

    cin >> n >> k;

    int countB = 0, countA = 0;
    swaps = 0;
    for ( int i = 0; i < 2 * n; i++ ) {
        char ch;
        cin >> ch;
        if ( ch == 'A' )
            countA++;
        else {
            countB++;
            swaps += max( 0, countB - countA );
            a[countB] = max( countA, countB );
            sumA[countB] = sumA[countB - 1] + a[countB];
            countLowerA[a[countB]]++;
            sumLowerA[a[countB]] += a[countB];
        }
    }
    for ( int i = 1; i <= n; i++ ) {
        countLowerA[i] += countLowerA[i - 1];
        sumLowerA[i] += sumLowerA[i - 1];
    }

    long long leftCost = -1, rightCost = 1e12;
    while ( rightCost - leftCost > 1 ) {
        long long cost = (leftCost + rightCost) / 2;

        computeDP( n, cost );

        if ( minGroups[n] > k )
            leftCost = cost;
        else
            rightCost = cost;
    }

    computeDP( n, rightCost );
    cout << swaps + minSwaps[n] - min( k, maxGroups[n] ) * rightCost;

    return 0;
}

• Subtask 1: 16 / 16
• Subtask 2: 24 / 24
• Subtask 3: 21 / 21
• Subtask 4: 0 / 26
• Subtask 5: 0 / 13