题解
代码
1 #include <cmath>
2 #include <cstdio>
3 #include <iostream>
4 #include <algorithm>
5 #define ll long long
6 using namespace std;
7 double a;
8 double dis(ll x,ll y) { return sqrt(x*x+y*y); }
9 ll cross(ll x1,ll y1,ll x2,ll y2) { return x1*y2-x2*y1; }
10 double getcos(ll x1,ll y1,ll x2,ll y2) { return (double)(x1*x2+y1*y2)/(dis(x1,y1)*dis(x2,y2)); }
11 int main()
12 {
13 freopen("math.in","r",stdin),freopen("math.out","w",stdout);
14 ll x1,y1,x2,y2,k;
15 while (scanf("%lld%lld%lld%lld",&x1,&y1,&x2,&y2)!=EOF)
16 {
17 if (cross(x1,y1,x2,y2)==0) { printf("0\n"); continue; }
18 while (1)
19 {
20 if (dis(x1,y1)>dis(x2,y2)) swap(x1,x2),swap(y1,y2);
21 a=getcos(x1,y1,x2,y2);
22 if (a<0) { x1=-x1,y1=-y1;continue; }
23 if (a<0.5) break;
24 k=dis(x2,y2)*a/dis(x1,y1)+0.5,x2-=k*x1,y2-=k*y1;
25 }
26 printf("%lld\n",min(x1*x1+y1*y1,x2*x2+y2*y2));
27 }
28 }
