题意：n个点的凸多边形，如果每个点都可在半径为 r的范围内移动，要保证仍为多边形，问 r最大为多少。
tags：水题，练练手
#include<bits/stdc++.h> using namespace std; #pragma comment(linker, "/STACK:102400000,102400000") #define rep(i,a,b) for (int i=a;i<=b;i++) #define per(i,b,a) for (int i=b;i>=a;i--) #define mes(a,b) memset(a,b,sizeof(a)) #define INF 0x3f3f3f3f #define MP make_pair #define PB push_back #define fi first #define se second #define eps 1e-6 typedef long long ll; const int N = 2005; int n; struct Point { double x, y; } p[N]; double dis(Point a, Point b) { return sqrt((a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y)); } double Heron(double a, double b, double c) { double p=(a+b+c)/2; return sqrt(p*(p-a)*(p-b)*(p-c)); } double getsqr(Point a, Point b, Point c) { return Heron(dis(a,b), dis(b,c), dis(a,c)); } int main() { scanf("%d", &n); rep(i,1,n) scanf("%lf %lf", &p[i].x, &p[i].y); p[n+1]=p[1], p[n+2]=p[2]; double ans=4.6e18; rep(i,3,n+2) { double len=getsqr(p[i-2], p[i-1], p[i])/dis(p[i-2],p[i]); ans=min(ans, len); } printf("%.6f ", ans); return 0; }