src/geometry/InsidePolygon.h

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• Last update: 2025-07-19 20:33:24+09:00
• Link: https://vlecomte.github.io/cp-geo.pdf

Depends on

• src/geometry/OnSegment.h
• src/geometry/Point.h
• src/geometry/SegmentDistance.h

Code

/**
 * Author: Victor Lecomte, chilli
 * Date: 2019-04-26
 * License: CC0
 * Source: https://vlecomte.github.io/cp-geo.pdf
 * Description: Returns true if p lies within the polygon. If strict is true,
 * it returns false for points on the boundary. The algorithm uses
 * products in intermediate steps so watch out for overflow.
 * Time: O(n)
 * Usage:
 * vector<P> v = {P{4,4}, P{1,2}, P{2,1}};
 * bool in = inPolygon(v, P{3, 3}, false);
 * Status: stress-tested and tested on kattis:pointinpolygon
 */
#pragma once

#include "src/geometry/Point.h"
#include "src/geometry/OnSegment.h"
#include "src/geometry/SegmentDistance.h"

template<class P>
bool inPolygon(vector<P> &p, P a, bool strict = true) {
	int cnt = 0, n = sz(p);
	rep(i,0,n) {
		P q = p[(i + 1) % n];
		if (onSegment(p[i], q, a)) return !strict;
		//or: if (segDist(p[i], q, a) <= eps) return !strict;
		cnt ^= ((a.y<p[i].y) - (a.y<q.y)) * a.cross(p[i], q) > 0;
	}
	return cnt;
}

Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/site-packages/onlinejudge_verify/documentation/build.py", line 71, in _render_source_code_stat
    bundled_code = language.bundle(stat.path, basedir=basedir, options={'include_paths': [basedir]}).decode()
                   ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/site-packages/onlinejudge_verify/languages/cplusplus.py", line 187, in bundle
    bundler.update(path)
    ~~~~~~~~~~~~~~^^^^^^
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/site-packages/onlinejudge_verify/languages/cplusplus_bundle.py", line 312, in update
    raise BundleErrorAt(path, i + 1, "#pragma once found in a non-first line")
onlinejudge_verify.languages.cplusplus_bundle.BundleErrorAt: src/geometry/InsidePolygon.h: line 15: #pragma once found in a non-first line

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