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#!/usr/local/bin/node
//
// See ../README.md
//
//
// Run as: node ch-2.js < input-file
//
//
// See https://stackoverflow.com/questions/2049582/
//
//
// This determines on which side of the line through (x1, y1) and
// (x2, y2) the origin lies. If > 0, then the origin lies to the left
// of the line, if < 0, the origin lies to the right of the line, if
// = 0, the origin lies on the line.
//
function side (x1, y1, x2, y2) {
return (y2 - y1) * x2 - (x2 - x1) * y2
}
require ('readline')
. createInterface ({input: process . stdin})
. on ('line', _ => {
//
// Parse input
//
let [x1, y1, x2, y2, x3, y3] = _ . split (/\s+/)
//
// Determine where the origin is relative to the three lines
// through the vertices of the triangle. Note we have to go
// in a specific order through the points. (Either clock wise,
// or counter clockwise, as long as we're consistent).
//
let s1 = side (x2, y2, x3, y3)
let s2 = side (x3, y3, x1, y1)
let s3 = side (x1, y1, x2, y2)
//
// If the origin either lies to the left (or on) each of the
// lines, or to the right (or on) each of the lines, the origin
// lies inside the triangle. If not, it does not.
//
console . log ((s1 <= 0 && s2 <= 0 && s3 <= 0) ||
(s1 >= 0 && s2 >= 0 && s3 >= 0) ? 1 : 0)
});
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