【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;
}