题目链接

http://acm.hdu.edu.cn/showproblem.php?pid=6136

题解

完了，普及题都不会做了。。。

发现一个重要性质是只有相邻的人才会相撞，于是直接拿堆维护即可。。。

WA了好几发。。。

代码

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<queue>
#include<algorithm>
#define llong long long
using namespace std;const int N = 1e5;
struct Fraction
{llong x,y;Fraction() {}Fraction(llong _x,llong _y) {x = _x,y = _y;}void output() {printf("%lld/%lld ",x,y);}bool operator <(const Fraction &arg) const{return x*arg.y<y*arg.x;}
};
struct Element
{llong a,b; int id;bool operator <(const Element &arg) const{return b<arg.b;}
} a[N+3];
struct Node
{int id1,id2; Fraction x;Node() {}Node(int _id1,int _id2,Fraction _x) {id1 = _id1,id2 = _id2,x = _x;}bool operator <(const Node &arg) const{return arg.x<x;}
};
priority_queue<Node> que;
bool vis[N+3];
int nxt[N+3],prv[N+3];
int n; llong m;llong gcd(llong x,llong y) {return y==0 ? x : gcd(y,x%y);}Fraction calc(Element x,Element y)
{if(x.a<y.a) {swap(x,y);}if(x.b>y.b) {y.b += m;}return Fraction(y.b-x.b,x.a-y.a);
}int main()
{int T; scanf("%d",&T);while(T--){scanf("%d%lld",&n,&m);for(int i=1; i<=n; i++) scanf("%lld",&a[i].b);for(int i=1; i<=n; i++) scanf("%lld",&a[i].a),a[i].id = i;sort(a+1,a+n+1);for(int i=1; i<=n; i++) prv[i] = i==1?n:i-1,nxt[i] = i==n?1:i+1;for(int i=1; i<=n; i++) que.push(Node(i,nxt[i],calc(a[i],a[nxt[i]])));Fraction ans;while(!que.empty()){Node cur = que.top(); que.pop();int u = cur.id1,v = cur.id2;if(vis[u]||vis[v]) continue;ans = cur.x;if(a[u].id>a[nxt[u]].id) swap(u,v);vis[u] = true;if(prv[u]!=nxt[u]){que.push(Node(prv[u],nxt[u],calc(a[prv[u]],a[nxt[u]])));}nxt[prv[u]] = nxt[u];prv[nxt[u]] = prv[u];}llong g = gcd(ans.x,ans.y);printf("%lld/%lld\n",ans.x/g,ans.y/g);for(int i=1; i<=n; i++) vis[i] = nxt[i] = prv[i] = 0;}return 0;
}