【codeforces 514B】Han Solo and Lazer Gun

【题目链接】:http://codeforces.com/contest/514/problem/B

【题意】



每次攻击可以把经过自己的一条直线上的所有点都毁掉;

然后给你n个目标物的坐标

问你最少要攻击多少次才能把所有目标物全部毁掉

【题解】



因为每个目标物都会毁掉：

则肯定要射一次的(如果它没有被毁掉的话);

把在这条线上的点全都毁掉就好;

没有什么最小攻击次数的概念.

判断点在直线上用向量搞就好;



【Number Of WA】



0



【完整代码】

#include <bits/stdc++.h>

using namespace std;

#define lson l,m,rt<<1

#define rson m+1,r,rt<<1|1

#define LL long long

#define rep1(i,a,b) for (int i = a;i <= b;i++)

#define rep2(i,a,b) for (int i = a;i >= b;i--)

#define mp make_pair

#define ps push_back

#define fi first

#define se second

#define rei(x) scanf("%d",&x)

#define rel(x) scanf("%lld",&x)

#define ref(x) scanf("%lf",&x)

#define ms(x,y) memset(x,y,sizeof x)

typedef pair<int,int> pii;

typedef pair<LL,LL> pll;

const int dx[9] = {0,1,-1,0,0,-1,-1,1,1};

const int dy[9] = {0,0,0,-1,1,-1,1,-1,1};

const double pi = acos(-1.0);

const int N = 1100;

struct point{

    int x,y;

    bool killed;

};

bool in(point a,point b,point c)

{

    return (b.x-a.x)*(c.y-a.y)==(c.x-a.x)*(b.y-a.y);

}

point a[N];

int x0,y0,n,ans = 0;

int main()

{

    //freopen("F:\\rush.txt","r",stdin);

    rei(n),rei(x0),rei(y0);

    rep1(i,1,n)

        rei(a[i].x),rei(a[i].y);

    rep1(i,1,n)

        if (a[i].killed==false)

        {

            a[i].killed = true;

            rep1(j,i+1,n)

                if (!a[j].killed && in(point{x0,y0},a[i],a[j]))

                {

                    a[j].killed=true;

                }

            ans++;

        }

    cout << ans << endl;

    //printf("\n%.2lf sec \n", (double)clock() / CLOCKS_PER_SEC);

    return 0;

}