52 lines
1.0 KiB
Go
52 lines
1.0 KiB
Go
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package aoc
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type Vector struct {
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Offset Point
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Scale int
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}
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func (v Vector) Point() Point {
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return v.Offset.Scale(v.Scale)
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}
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type Point [2]int
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func (p Point) Add(a Point) Point {
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return Point{p[0] + a[0], p[1] + a[1]}
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}
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func (p Point) Scale(m int) Point {
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return Point{p[0] * m, p[1] * m}
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}
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func Transpose[T any](matrix [][]T) [][]T {
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rows, cols := len(matrix), len(matrix[0])
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m := make([][]T, cols)
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for i := range m {
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m[i] = make([]T, rows)
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}
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for i := 0; i < cols; i++ {
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for j := 0; j < rows; j++ {
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m[i][j] = matrix[j][i]
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}
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}
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return m
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}
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// NumPoints the number of the points inside an outline plus the number of points in the outline
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func NumPoints(outline []Point, borderLength int) int {
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// shoelace - find the float area in a shape
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sum := 0
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for _, p := range Pairwise(outline) {
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row1, col1 := p[0][0], p[0][1]
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row2, col2 := p[1][0], p[1][1]
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sum += row1*col2 - row2*col1
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}
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area := sum / 2
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// pick's theorem - find the number of points in a shape given its area
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return (ABS(area) - borderLength/2 + 1) + borderLength
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}
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