Submission #1047440

#	Time	Username	Problem	Language	Result	Execution time	Memory
1047440		sofijavelkovska	Event Hopping (BOI22_events)	C++17	25 / 100	1268 ms	100616 KiB

events

#include <bits/stdc++.h>
using namespace std;

const int MAXN=5e3, INF=1e9;

int n;
int l[MAXN], r[MAXN];

bool rcompare(int x, int y)
{
    if (r[x]==r[y])
        return l[x]<l[y];

    return r[x]<r[y];
}

bool lcompare(int x, int y)
{
    if (l[x]<l[y])
        return true;

    return false;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int q;
    cin >> n >> q;
    for (int i=0; i<n; i++)
        cin >> l[i] >> r[i];
    int sorted[n];
    for (int i=0; i<n; i++)
        sorted[i]=i;
    sort(sorted, sorted+n, rcompare);
    int ranked[n];
    for (int i=0; i<n; i++)
        ranked[sorted[i]]=i;
    map<int, int> compress;
    for (int i=0; i<n; i++)
    {
        compress[l[i]]=0;
        compress[r[i]]=0;
    }
    int counter=0;
    for (auto x : compress)
    {
        compress[x.first]=counter;
        counter=counter+1;
    }
    int lsorted[n];
    for (int i=0; i<n; i++)
        lsorted[i]=i;
    sort(lsorted, lsorted+n, lcompare);
    int answer[n][n];
    for (int i=0; i<n; i++)
        for (int j=0; j<n; j++)
        {
            if (i==j)
                answer[i][j]=0;
            else if (r[i]==r[j])
                answer[i][j]=1;
            else
                answer[i][j]=-1;
        }
    for (int y=0; y<n; y++)
    {
        int dp[n];
        dp[ranked[y]]=0;
        multiset<int> best;
        best.insert(0);
        //update(0, 0, MAXN, compress[l[y]], 0);
        int t=n-1;
        for (int i=ranked[y]-1; i>=0; i--)
        {
            while (t>=0 && l[lsorted[t]]>r[sorted[i]])
            {
                if (ranked[lsorted[t]]<=ranked[y] && dp[ranked[lsorted[t]]]!=INF)
                    best.erase(best.find(dp[ranked[lsorted[t]]]));
                t=t-1;
            }
            dp[i]=INF;
            if (!best.empty())
                dp[i]=*best.begin()+1;
            if (dp[i]!=INF)
                best.insert(dp[i]);
            if (dp[i]!=INF)
                answer[sorted[i]][y]=dp[i];
            //cout << "l r " << l[sorted[i]] << ' ' << r[sorted[i]] << '\n';
            //cout << "find " << find(0, 0, MAXN, 0, compress[r[sorted[i]]]+1) << '\n';
            //update(0, 0, MAXN, compress[l[sorted[i]]], dp[i]);
            //cout << "dp " << dp[i] << '\n';
        }
    }
    //for (int i=0; i<n; i++)
      //  for (int j=0; j<n; j++)
        //    cout << i+1 << ' ' << j+1 << ' ' << answer[i][j] << '\n';
    while (q--)
    {
        int x, y;
        cin >> x >> y;
        x=x-1;
        y=y-1;
        if (answer[x][y]!=-1)
            cout << answer[x][y] << '\n';
        else
            cout << "impossible" << '\n';
    }

    return 0;
}



/*#include <bits/stdc++.h>
using namespace std;

const int MAXN=1e5, LOG=17;

int n;
int l[MAXN], r[MAXN];

bool rcompare(int x, int y)
{
    if (r[x]<r[y])
        return true;

    return false;
}

bool lcompare(int x, int y)
{
    if (l[x]<l[y])
        return true;

    return false;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int q;
    cin >> n >> q;
    for (int i=0; i<n; i++)
        cin >> l[i] >> r[i];
    int sorted[n];
    for (int i=0; i<n; i++)
        sorted[i]=i;
    sort(sorted, sorted+n, rcompare);
    int ranked[n];
    for (int i=0; i<n; i++)
        ranked[sorted[i]]=i;
    int lsorted[n];
    for (int i=0; i<n; i++)
        lsorted[i]=i;
    sort(lsorted, lsorted+n, lcompare);
    int t=n-1;
    set<int> farthest;
    for (int i=0; i<n; i++)
        farthest.insert(i);
    int blift[n][LOG];
    for (int i=0; i<n; i++)
        for (int j=0; j<LOG; j++)
            blift[i][j]=-1;
    for (int i=n-1; i>=0; i--)
    {
        while (t>=0 && l[lsorted[t]]>r[sorted[i]])
        {
            farthest.erase(ranked[lsorted[t]]);
            t=t-1;
        }
        auto it=farthest.end();
        it--;
        if (*it!=i)
            blift[i][0]=*it;
    }
    for (int j=1; j<LOG; j++)
        for (int i=0; i<n; i++)
            if (blift[i][j-1]!=-1 && blift[blift[i][j-1]][j-1]!=-1)
                blift[i][j]=blift[blift[i][j-1]][j-1];
    while (q--)
    {
        int x, y;
        cin >> x >> y;
        x=ranked[x-1];
        y=ranked[y-1];
        if (x>y)
        {
            cout << "impossible" << '\n';
            continue;
        }
        if (x==y)
        {
            cout << 0 << '\n';
            continue;
        }
        int total=0;
        for (int j=LOG-1; j>=0; j--)
        {
            if (blift[x][j]!=-1 && blift[x][j]<y)
            {
                x=blift[x][j];
                total=total+(1<<j);
            }
        }
        if (blift[x][0]>=y)
            cout << total+1 << '\n';
        else
            cout << "impossible" << '\n';
    }

    return 0;
}*/

• Subtask 1: 0 / 10
• Subtask 2: 10 / 10
• Subtask 3: 15 / 15
• Subtask 4: 0 / 15
• Subtask 5: 0 / 20
• Subtask 6: 0 / 30