Merge pull request #318 from vaskoz/day151

Day151

README.md

@@ -161,3 +161,4 @@ problems from
 * [Day 148](https://github.com/vaskoz/dailycodingproblem-go/issues/309)
 * [Day 149](https://github.com/vaskoz/dailycodingproblem-go/issues/311)
 * [Day 150](https://github.com/vaskoz/dailycodingproblem-go/issues/312)
+* [Day 151](https://github.com/vaskoz/dailycodingproblem-go/issues/313)

day151/problem.go

@@ -0,0 +1,31 @@
+package day151
+
+// PixelGrid is a 2-D grid of pixel colors.
+type PixelGrid [][]Color
+
+// Coordinate represents a pixel location in the grid.
+type Coordinate struct {
+	Row, Col int
+}
+
+// Color represents a unique color that a pixel can have.
+type Color rune
+
+// ReplaceAdjacentColorPixel changes all the pixels adjacent to the given coordinate
+// of the same color to the new color.
+func ReplaceAdjacentColorPixel(grid PixelGrid, c Coordinate, color Color) {
+	start := grid[c.Row][c.Col]
+	replaceAdjacentColorPixel(grid, c, start, color)
+}
+
+func replaceAdjacentColorPixel(grid PixelGrid, c Coordinate, start, target Color) {
+	if c.Row < 0 || c.Col < 0 || c.Row >= len(grid) || c.Col >= len(grid[0]) {
+		return
+	} else if grid[c.Row][c.Col] == start {
+		grid[c.Row][c.Col] = target
+		replaceAdjacentColorPixel(grid, Coordinate{c.Row - 1, c.Col}, start, target) // up
+		replaceAdjacentColorPixel(grid, Coordinate{c.Row + 1, c.Col}, start, target) // down
+		replaceAdjacentColorPixel(grid, Coordinate{c.Row, c.Col - 1}, start, target) // left
+		replaceAdjacentColorPixel(grid, Coordinate{c.Row, c.Col + 1}, start, target) // right
+	}
+}

day151/problem_test.go

@@ -0,0 +1,58 @@
+package day151
+
+import (
+	"reflect"
+	"testing"
+)
+
+var testcases = []struct {
+	grid     PixelGrid
+	coord    Coordinate
+	color    Color
+	expected PixelGrid
+}{
+	{
+		PixelGrid{
+			[]Color("BBW"),
+			[]Color("WWW"),
+			[]Color("WWW"),
+			[]Color("BBB"),
+		},
+		Coordinate{2, 2},
+		Color('G'),
+		PixelGrid{
+			[]Color("BBG"),
+			[]Color("GGG"),
+			[]Color("GGG"),
+			[]Color("BBB"),
+		},
+	},
+}
+
+func TestReplaceAdjacentColorPixel(t *testing.T) {
+	t.Parallel()
+	for _, tc := range testcases {
+		testGrid := copyGrid(tc.grid)
+		ReplaceAdjacentColorPixel(testGrid, tc.coord, tc.color)
+		if !reflect.DeepEqual(tc.expected, testGrid) {
+			t.Errorf("Expected %v got %v", tc.expected, testGrid)
+		}
+	}
+}
+
+func BenchmarkReplaceAdjacentColorPixel(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			testGrid := copyGrid(tc.grid)
+			ReplaceAdjacentColorPixel(testGrid, tc.coord, tc.color)
+		}
+	}
+}
+
+func copyGrid(grid PixelGrid) PixelGrid {
+	var newGrid PixelGrid
+	for i := range grid {
+		newGrid = append(newGrid, append([]Color{}, grid[i]...))
+	}
+	return newGrid
+}