CodeForces - 514B Han Solo and Lazer Gun
題意：
? ? ? ? 給出N個點，和起始點X0，Y0，求N個點中有幾組不同斜率與原點連接后斜率不同的點
思路：
? ? ? ? 考慮到可能出現的精度丟失，使用的分數的形式表示每個斜率，再用map去重就可以了
代碼：
#include <iostream> #include <map> using namespace std;int n,w,z,x0,y0;int gcd(int x,int y){if(y) return gcd(y,x%y);return x; } int main() {ios::sync_with_stdio(false);while(cin>>n){cin>>x0>>y0;map <pair<int,int>,int > mp;int ans=0;while(n--){cin>>w>>z;w-=x0;z-=y0;int temp=gcd(w,z);w/=temp;z/=temp;if(!mp[make_pair(w,z)]++)ans++;}cout<<ans<<endl;} }There are?n?Imperial stormtroopers on the field. The battle field is a plane with Cartesian coordinate system. Each stormtrooper is associated with his coordinates(x,?y)?on this plane.
Han Solo has the newest duplex lazer gun to fight these stormtroopers. It is situated at the point?(x0,?y0). In one shot it can can destroy all the stormtroopers, situated on some line that crosses point?(x0,?y0).
Your task is to determine what minimum number of shots Han Solo needs to defeat all the stormtroopers.
The gun is the newest invention, it shoots very quickly and even after a very large number of shots the stormtroopers don't have enough time to realize what's happening and change their location.
The first line contains three integers?n,?x0?и?y0?(1?≤?n?≤?1000,??-?104?≤?x0,?y0?≤?104) — the number of stormtroopers on the battle field and the coordinates of your gun.
Next?n?lines contain two integers each?xi,?yi?(?-?104?≤?xi,?yi?≤?104) — the coordinates of the stormtroopers on the battlefield. It is guaranteed that no stormtrooper stands at the same point with the gun. Multiple stormtroopers can stand at the same point.
Print a single integer — the minimum number of shots Han Solo needs to destroy all the stormtroopers.
Explanation to the first and second samples from the statement, respectively:
總結
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