Submission #1047375

#	Time	Username	Problem	Language	Result	Execution time	Memory
1047375		sofijavelkovska	Event Hopping (BOI22_events)	C++17	0 / 100	1590 ms	11076 KiB

events

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

const int MAXN=(1<<18), INF=1e9;

int n;
int l[MAXN], r[MAXN];
int tree[2*MAXN-1];

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

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

int find(int x, int l, int r, int lt, int rt)
{
    if (l>=rt || r<=lt)
        return INF;
    if (l>=lt && r<=rt)
        return tree[x];

    return min(find(2*x+1, l, (l+r)/2, lt, rt), find(2*x+2, (l+r)/2, r, lt, rt));
}

void update(int x, int l, int r, int index, int value)
{
    if (l>index || r<=index)
        return;
    if (r-l==1)
    {
        tree[x]=value;
        return;
    }
    update(2*x+1, l, (l+r)/2, index, value);
    update(2*x+2, (l+r)/2, r, index, value);
    tree[x]=min(tree[2*x+1], tree[2*x+2]);

    return;
}

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;
    }
    while (q--)
    {
        int x, y;
        cin >> x >> y;
        x=x-1;
        y=y-1;
        if (x==y)
        {
            cout << 0 << '\n';
            continue;
        }
        if (r[x]>r[y])
        {
            cout << "impossible" << '\n';
            continue;
        }
        if (r[x]==r[y])
        {
            cout << 1 << '\n';
            continue;
        }
        for (int i=0; i<2*MAXN-1; i++)
            tree[i]=INF;
        int dp[n];
        dp[ranked[y]]=0;
        update(0, 0, MAXN, compress[l[y]], 0);
        for (int i=ranked[y]-1; i>=0; i--)
        {
            dp[i]=min(INF, find(0, 0, MAXN, compress[l[sorted[i]]], compress[r[sorted[i]]]+1)+1);
            //cout << "l r " << l[sorted[i]] << ' ' << r[sorted[i]] << '\n';
            update(0, 0, MAXN, compress[l[sorted[i]]], dp[i]);
            //cout << "dp " << dp[i] << '\n';
        }
        if (dp[ranked[x]]!=INF)
            cout << dp[ranked[x]] << '\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: 0 / 10
• Subtask 3: 0 / 15
• Subtask 4: 0 / 15
• Subtask 5: 0 / 20
• Subtask 6: 0 / 30