Submission #850891

#	Time	Username	Problem	Language	Result	Execution time	Memory
850891		danikoynov	Chorus (JOI23_chorus)	C++14	61 / 100	2800 ms	207868 KiB

chorus

/**
 ____ ____ ____ ____ ____ ____
||l |||e |||i |||n |||a |||d ||
||__|||__|||__|||__|||__|||__||
|/__\|/__\|/__\|/__\|/__\|/__\|

**/

#include<bits/stdc++.h>
#define endl '\n'

using namespace std;
typedef long long ll;

void speed()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
}

const int maxn = 5100;
int n, k;
string s;

int dp[maxn][maxn], pos[2][maxn], pref[maxn];
/**

*/

void chmin(int &var, int val) /// careful for long long
{
    var = min(var, val);
}

///int cost[maxn][maxn];

void precalc()
{
    for (int j = 1; j <= n; j ++)
    {
        int tk = 0;
        for (int fix = 1; fix <= n - j; fix ++)
        {
                if (pos[0][fix + j] > j * 2 + fix)
                    tk += pos[0][fix + j] - (j * 2 + fix);
            ///cost[j + 1][j + fix] = tk;
        }
    }
}

int cost(int left, int right)
{
    int above = (left - 1) * 2;
    int lf = left, rf = right;
    while(lf <= rf)
    {
        int mf = (lf + rf) / 2;
        if (pos[0][mf] > above + (mf - left + 1))
            rf = mf - 1;
        else
            lf = mf + 1;
    }

    int sum = pref[right] - pref[lf - 1];
    sum = sum - (right - lf + 1) * above;
    int len = right - left + 1;
    int sm = lf - left;
    sum = sum - (len) * (len + 1) / 2;
    sum = sum + (sm) * (sm + 1) / 2;
    /**for (int i = lf; i <= right; i ++)
    {

            sum = sum + pos[0][i] - (above + (i - left + 1));
    }*/
    return sum;

}

void divide(int row, int left, int right, int optl, int optr)
{
    if (left > right)
        return;

    int mid = (left + right) / 2;
    int opt = -1;
    for (int j = optl; j <= min(optr, mid); j ++)
    {
        int cur =dp[j - 1][row - 1] + cost(j, mid);
        if (cur < dp[mid][row])
        {
            dp[mid][row] = cur;
            opt = j;
        }
    }

    divide(row, left, mid - 1, optl, opt);
    divide(row, mid + 1, right, opt, optr);
}
void solve()
{
    cin >> n >> k >> s;

    s = "#" + s;
    int cntA = 0, cntB = 0;
    for (int i = 1; i <= 2 * n; i ++)
    {
        if (s[i] == 'A')
        {
            cntA ++;
            pos[0][cntA] = i;
            pref[cntA] = pref[cntA - 1] + i;
        }
        else
        {
            cntB ++;
            pos[1][cntB] = i;
        }
    }

    for (int i = 0; i <= n; i ++)
        for (int j = 0; j <= n; j ++)
        dp[i][j] = 4 * n * n; /// careful for overflow

 precalc();

        int cr = 0;
    for (int j = 1; j <= n; j ++)
    {
        cr = cr + pos[0][j] - j;

        dp[j][1] = cr;
    }

    for (int j = 2; j <= k; j ++)

    {
        divide(j, j, n, j, n);
    }
    /**for (int i = 1; i <= n; i ++)
        for (int j = 2; j <= k; j ++)
    {
        for (int fix = 1; fix <= i; fix ++)
        {
            if (dp[i - fix][j - 1] != 4 * n * n)
            {
                dp[i][j] = min(dp[i][j], dp[i - fix][j - 1] + cost(i - fix + 1, i));
            }
        }
    }*/


    int ans = 4 * n * n;
    for (int i = 1; i <= k; i ++)
        ans = min(ans, dp[n][i]);
    cout << ans << endl;
}

int main()
{
    speed();
    ///freopen("test.txt", "r", stdin);
    solve();
    return 0;
}

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