Create 1249_qq_21110267.cpp

CodeVS/1249_qq_21110267.cpp

@@ -0,0 +1,46 @@
+#include<cstdio>
+#include<cmath>
+#include<vector>
+#include<algorithm>
+using namespace std;
+
+const int maxn = 100 + 10;
+int n;
+
+struct Point {
+    int x, y;
+    Point(int x=0, int y=0):x(x),y(y) {}
+}P[maxn];
+
+typedef Point Vector;
+
+Vector operator + (Vector A, Vector B) { return Vector(A.x+B.x, A.y+B.y); }
+Vector operator - (Vector A, Vector B) { return Vector(A.x-B.x, A.y-B.y); }
+Vector operator * (Vector A, int p) { return Vector(A.x*p, A.y*p); }
+Vector operator / (Vector A, int p) { return Vector(A.x/p, A.y/p); }
+
+bool operator < (const Vector& a, const Vector& b) {
+    return a.x < b.x || (a.x == b.x && a.y < b.y);
+}
+
+int Dot(Vector A, Vector B) { return A.x*B.x + A.y*B.y; }
+int Length(Vector A) { return sqrt(Dot(A, A)); }
+int Angle(Vector A, Vector B) { return acos(Dot(A, B) / Length(A) / Length(B)); }
+int Cross(Vector A, Vector B) { return A.x*B.y - A.y*B.x; }
+int Area2(Point A, Point B, Point C) { return Cross(B-A, C-A); }
+
+int PolygonArea() {
+    int area = 0;
+    for(int i = 1; i < n-1; i++) 
+        area += Cross(P[i]-P[0], P[i+1]-P[0]);
+    return area/2;
+}
+
+int main() {
+    scanf("%d", &n);
+    for(int i = 0; i < n; i++) 
+        scanf("%d%d", &P[i].x, &P[i].y);
+
+    printf("%d\n", PolygonArea());
+    return 0;
+}