Contest 176 - LeetCode 1353. Maximum Number of Events That Can Be Attended (贪心)

struct Node
{
    int l;
    int r;
}b[100005];
int cmp(Node a,Node b)
{
    if(a.r==b.r)
        return a.l>b.l;
    return a.r<b.r;
}
class Solution {
public:
    int vis[100005];
    int maxEvents(vector<vector<int>>& events) {
        
        int len = 0;
        int p = 0;
        for(int i=0;i<events.size();i++)
        {
           len=max(len,events[i][1]);
           b[p].l = events[i][0];
           b[p].r = events[i][1];
           p++;
        }
        
        sort(b,b+p,cmp);
        
        int ans=0;
        for(int i=0;i<p;i++)
        {
            for(int j=b[i].l;j<=b[i].r;j++)
            {
                if(!vis[j])
                {
                    vis[j]=1;
                    ans++;
                    break;
                }
            }
        }
        return ans;
        
    }
};

struct Node
{
    int l;
    int r;
}b[100005];
int cmp(Node a,Node b)
{
    if(a.r==b.r)
        return a.l>b.l;
    return a.r<b.r;
}
class Solution {
public:
    int num[100005*4];
    int maxEvents(vector<vector<int>>& events) {
        
        int len = 0;
        int p = 0;
        for(int i=0;i<events.size();i++)
        {
           len=max(len,events[i][1]);
           b[p].l = events[i][0];
           b[p].r = events[i][1];
           p++;
        }
        
        sort(b,b+p,cmp);
        
        int ans=0;
        for(int i=0;i<p;i++)
        {
            int pos = query(1,1,len,b[i].l,b[i].r,0);
            if(pos!=-1)
            {
                ans++;
                update(1,1,len,pos,1);
            }
        }
        return ans;
        
    }
    
    void pushup(int node)
    {
        if(num[node<<1]==num[node<<1|1])
            num[node]=num[node<<1];
        else
            num[node]=-1;
    }
    
    void update(int node,int l,int r,int i,int val)
    {
        if(l==r&&l==i)
        {
            num[node]=val;
            return;
        }
        
        int mid = (l+r)/2;
        
        if(i<=mid)
            update(node<<1,l,mid,i,val);
        if(i>mid)
            update(node<<1|1,mid+1,r,i,val);
        
        pushup(node);
    }
    
    int query(int node,int l,int r,int start,int end,int val)
    {
        if(start<=l&&r<=end)
        {
            if(num[node]!=-1)
            {
                if(num[node]==val)
                    return l;
                else
                    return -1;
            }
        }
        
        int mid = (l+r)/2;
        
        int res;
        if(start<=mid)
        {
            res = query(node<<1,l,mid,start,end,val);
            if(res!=-1)
                return res;
        }
        
        if(end>mid)
        {
            res = query(node<<1|1,mid+1,r,start,end,val);
        }
        
        return res;
    }
};