题意
给出一系列点，求这个多边形面积
思路 向量叉积
AC代码
#include <cstdio> #include <cstring> #include <ctype.h> #include <cstdlib> #include <iostream> #include <algorithm> #include <cmath> #include <deque> #include <vector> #include <queue> #include <string> #include <map> #include <stack> #include <set> #include <numeric> #include <sstream> using namespace std; typedef long long LL; const double PI = 3.14159265358979323846264338327; const double E = 2.718281828459; const double eps = 1e-6; const int MAXN = 0x3f3f3f3f; const int MINN = 0xc0c0c0c0; const int maxn = 1e2 + 5; const int MOD = 1e9 + 7; struct Node { double x; double y; }G[maxn]; double Cross(Node a, Node b) { return a.x * b.y - a.y * b.x; } int main() { int t; cin >> t; while (t--) { int n; cin >> n; for (int i = 0; i < n; i++) scanf("%lf%lf", &G[i].x, &G[i].y); double sum = 0; G[n].x = G[0].x; G[n].y = G[0].y; for (int i = 0; i < n; i++) sum += Cross(G[i], G[i + 1]); sum = sum / 2.0; cout << sum << endl; } }转载于:https://www.cnblogs.com/Dup4/p/9433277.html
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