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  • 【C++竞赛 G】Lines

    Time Limit: 3s Memory Limit: 64MB
    问题描述
    Ljr has several lines. The lines are covered on the X axis. Let A is a point which is covered by the most lines. Ljr wants to know how many lines cover A.
    输入描述
    The first line contains a single integer T(1≤T≤100) (the data for N>100 less than 10 cases), indicating the number of test cases. Each test case begins with an integerN(1≤N≤〖10〗^5), indicating the number of lines. Next N lines contains two integers X_i and Y_i (-〖10〗^9≤X_i,Y_i≤〖10〗^9), describing a line.
    输出描述
    For each case, output an integer means how many lines cover A.
    输入样例
    2
    5
    1 2
    2 3
    2 4
    3 4
    5 1000
    5
    1 2
    3 4
    5 6
    7 8
    9 10
    输出样例
    3
    1
    ?
    【题目链接】:

    【题解】

    把区间端点离散化一下,然后就转换成区间最大值的问题了;
    写个线段树就好;
    x<=y不一定成立;

    【完整代码】

    #include <bits/stdc++.h>
    #define rep1(i,a,b) for (int i = a;i <= b;i++)
    using namespace std;
    #define pb push_back;
    
    const int MAXN = 1e5+10;
    
    int ma[MAXN*2*4],tag[MAXN*2*4];
    struct abc
    {
        int l,r;
    };
    
    abc aa[MAXN];
    vector <int> a;
    map <int,int> dic;
    
    void push_down(int rt)
    {
        tag[rt<<1]+=tag[rt];
        tag[rt<<1|1]+=tag[rt];
        ma[rt<<1]+=tag[rt];
        ma[rt<<1|1]+=tag[rt];
        tag[rt] = 0;
    }
    
    void up_data(int L,int R,int l,int r,int rt)
    {
        //printf("%d %d
    ",l,r);
        if (L<=l && r <= R)
        {
            ma[rt]++;
            tag[rt]++;
            return;
        }
        if (tag[rt]!=0)
            push_down(rt);
        int m = (l+r)>>1;
        if (L<=m)
            up_data(L,R,l,m,rt<<1);
        if (m<R)
            up_data(L,R,m+1,r,rt<<1|1);
        ma[rt] = max(ma[rt<<1],ma[rt<<1|1]);
    }
    
    int main()
    {
        //freopen("D:\rush.txt","r",stdin);
        int T;
        scanf("%d",&T);
        while (T--)
        {
            memset(ma,0,sizeof(ma));
            memset(tag,0,sizeof(tag));
            dic.clear();
            a.clear();
            int n;
            scanf("%d",&n);
            rep1(i,1,n)
            {
                scanf("%d%d",&aa[i].l,&aa[i].r);
                if (aa[i].l>aa[i].r)
                    swap(aa[i].l,aa[i].r);
                if (!dic[aa[i].l])
                {
                    a.push_back(aa[i].l);
                    dic[aa[i].l] = 1;
                }
                if (!dic[aa[i].r])
                {
                    a.push_back(aa[i].r);
                    dic[aa[i].r] = 1;
                }
            }
            sort(a.begin(),a.end());
            rep1(i,1,n)
            {
                int l,r;
                l = lower_bound(a.begin(),a.end(),aa[i].l)-a.begin()+1;
                r = lower_bound(a.begin(),a.end(),aa[i].r)-a.begin()+1;
                up_data(l,r,1,MAXN<<1,1);
            }
    
            printf("%d
    ",ma[1]);
        }
        return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/AWCXV/p/7626870.html
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