题目链接：Minimal Area
题意：按逆时针给你凸多边形的所有点，让你选三个点使得得到的三角形面积最小。
思路：不难证明相邻的三个点是面积最小的，然后叉乘直接计算取最小值就可以。
#include<iostream>#include<cstdio>#include<cstring>#include<cstdlib>#include<cmath>#include<algorithm>#include<queue>#include<stack>#include<vector>#include<map>#include<set>#define inf 0x3f3f3f3f3f3f3f3fusing namespace std;typedef long long ll;const int N = 200010;struct node{ ll x, y;} s[N];int main(){ ll n; scanf("%lld", &n); for(int i = 0; i < n; i++) { scanf("%lld %lld", &s[i].x, &s[i].y); } ll ans = inf; for(int i = 0; i < n; i++) { ll x1 = s[(i-1+n)%n].x-s[(i-2+n)%n].x; ll y1 = s[(i-1+n)%n].y-s[(i-2+n)%n].y; ll x2 = s[i].x-s[(i-1+n)%n].x; ll y2 = s[i].y-s[(i-1+n)%n].y; ll now = abs(x1*y2-x2*y1); ans = min(ans, now); } printf("%lldn", ans); return 0;}