HLG 1400 汽车比赛

题目链接：http://acm.hrbust.edu.cn/index.php?m=ProblemSet&a=showProblem&problem_id=1400

结构体排序+树状数组模板..

#include<cstdio>

#include<cstring>

#include<algorithm>

using namespace std;

int c[100009];

struct point

{

    int x;

    int v;

} p[100000];

bool cmp(point p1,point p2)

{



    if(p1.x !=p2.x)

        return p1.x>p2.x;

    else

        return p1.v<p2.v;

}

int lowbit(int x)

{

    return x & (-x);

}

void update(int i,int val)

{

    while(i<=100000)

    {

        c[i]+=val;

        i+=lowbit(i);

    }



}

int Sum(int i)

{

    int s=0;

    while(i>0)

    {

        s += c[i];

        i -= lowbit(i);

    }

    return s;

}

int main()

{

    //freopen("input.txt","r",stdin);

    int i,n;

    while(scanf("%d",&n)!=EOF)

    {



        memset(c,0,sizeof(c));

        long long int ans = 0;

        for(i=0; i<n; i++)

            scanf("%d%d",&p[i].x,&p[i].v);

        sort(p,p+n,cmp);

        for(i=0; i<n; i++)

        {

            ans += Sum(p[i].v);

            update(p[i].v+1,1);

        }

        printf("%lld\n",ans);

    }

    return 0;

}