UVALive

题目链接点这里

对于判断点是否在凸多边形内有logn的算法，，可以看这一篇博客

HLG 1429 凸多边形【快速判断点在凸多边形内】

#include<iostream>#include<cstdio>#include<math.h>#include<algorithm>#include<map>#include<set>#include<bitset>#include<stack>#include<queue>#include<string.h>#include<cstring>#include<vector>#include<time.h>#include<stdlib.h>using namespace std;#define INF 0x3f3f3f3f#define INFLL 0x3f3f3f3f3f3f3f3f#define FIN freopen("input.txt","r",stdin);#define sf(x,y) scanf("x",y)#define pf(x,y) printf("x",y)#define mem(x,y) memset(x,y,sizeof(x))typedef unsigned long long ULL;typedef long long LL;#define fuck(x) cout<<"["<<x<<"]"<<endl;#define lson l,m,rt<<1#define rson m+1,r,rt<<1|1typedef pair<pair<LL,LL>,LL> PIII;typedef pair<LL,LL> PII;const int MX=1e4+10;double eps=1e-8;int L,S;struct Point {    double x, y;    Point() {}    Point(double x,double y):x(x),y(y) {}    bool operator<(const Point&b) const {        if(x != b.x) return x < b.x;        return y < b.y;    }    Point operator-(const Point &P) const {        return Point(x - P.x, y - P.y);;    }    double operator^(const Point &P) const { //叉积        return x * P.y - y * P.x;//如果改成整形记得加LL    }    double operator*(const Point &P) const { //点积        return x * P.x + y * P.y;//如果改成整形记得加LL    }};typedef Point Vector;int sign(double x) {    if(fabs(x)<eps)return 0;    return x<0?-1:1;}int dcmp(double a,double b) {    if(fabs(a-b)<eps)return 0;    else if(a>b)return 1;    else return -1;}Point P[MX], R[MX];int convex(int n) {    int m = 0, k;    sort(P, P + n);    for(int i = 0; i < n; i++) {        while(m > 1 && sign((R[m - 1]-R[m-2])^(P[i]-R[m - 2]))<= 0) m--;        R[m++] = P[i];    }    k = m;    for(int i = n - 2; i >= 0; i--) {        while(m > k && sign((R[m - 1]-R[m-2])^(P[i]-R[m - 2]))<= 0) m--;        R[m++] = P[i];    }    if(n > 1) m--;    return m;}//nlogn计算x是否在凸多边形内int is_in(Point P,Point *R,int n) { //-1不在，0在边上，1在内部    int l=1, r=n-2,mid;    while(l<=r) {        mid = (l+r) >> 1;        int t1 = sign((R[mid]-R[0])^(P-R[0]));        int t2 = sign((R[mid+1]-R[0])^(P-R[0]));        if(t1>=0 &&t2<=0) {            int t3=sign((P-R[mid])^(P-R[mid+1]));            if(t3 < 0) return -1;            else if(t1||t2||t3)return 0;            return 1;        } else if(t1 < 0)r = mid -1;        else l = mid+1;    }    return -1;}int main() {    FIN;    while(~scanf("%d",&L)) {        for(int i=0; i<L; i++)scanf("%lf%lf",&P[i].x,&P[i].y);        L=convex(L);        scanf("%d",&S);        int ans=0;        for(int i=0; i<S; i++) {            double x,y;            scanf("%lf%lf",&x,&y);            if(is_in(Point(x,y),R,L)>=0)ans++;        }        cout<<ans<<endl;    }    return 0;}