Submission #906456

#	Time	Username	Problem	Language	Result	Execution time	Memory
906456		LucaIlie	Chorus (JOI23_chorus)	C++17	0 / 100	2 ms	8540 KiB

chorus

#include <bits/stdc++.h>

using namespace std;

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

void computeDP( int n, long long cost ) {
    for ( int i = 1; i <= n; i++ )
        minSwaps[i] = (long long)n * cost + 1;

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

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 = 0, 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] - minGroups[n] * rightCost;

    return 0;
}

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