15-yuyu0830

15-yuyu0830

yuyu0830/README.md

@@ -15,4 +15,5 @@
 | 11차시| 2024.05.08 |  그리디  | [연료 채우기](https://www.acmicpc.net/problem/1826)  | - |
 | 12차시| 2024.05.13 |  해시  | [두 배열의 합](https://www.acmicpc.net/problem/2143)  | - |
 | 13차시| 2024.05.21 |  LIS  | [가장 긴 증가하는 부분 수열 2](https://www.acmicpc.net/problem/12015)  | - |
+| 15차시| 2024.06.01 |  기하  | [다각형의 면적](https://www.acmicpc.net/problem/2166)  | - |
 ---

yuyu0830/수학/2166.cpp

@@ -0,0 +1,51 @@
+#include <iostream>
+#include <vector>
+#define MAX 99999999
+
+using namespace std;
+
+typedef long long ll;
+
+struct Point {
+    ll x, y;
+    Point(ll X, ll Y) : x(X), y(Y) {};
+};
+
+ll getArea(Point a, Point b) {
+    ll square = abs((a.x - b.x) * min(abs(a.y), abs(b.y))) * 2;
+    ll triangle = abs((a.x - b.x) * (a.y - b.y));
+
+    return square + triangle;
+}
+
+vector<Point> v;
+
+int main() {
+    ll a, b, area = 0, mx = MAX, my = MAX;
+
+    int n; cin >> n;
+
+    for (int i = 0; i < n; i++) {
+        cin >> a >> b;
+        v.push_back(Point(a, b));
+
+        mx = min(mx, a);
+        my = min(my, b);
+    }
+
+    for (auto &p : v) {
+        p.x -= mx;
+        p.y -= my;
+    }
+
+    v.push_back(v[0]);
+
+    for (int i = 0; i < n; i++) {
+        Point cur = v[i];
+        Point next = v[i + 1];
+
+        area += getArea(cur, next) * (cur.x <= next.x ? 1 : -1);
+    }
+
+    printf("%.1f\n", abs((double) area / 2));
+}