Merge 9474e8e into 94c05f1

README.md

@@ -106,4 +106,5 @@ problems from
 * [Day 95](https://github.com/vaskoz/dailycodingproblem-go/issues/198)
 * [Day 96](https://github.com/vaskoz/dailycodingproblem-go/issues/200)
 * [Day 97](https://github.com/vaskoz/dailycodingproblem-go/issues/203)
+* [Day 98](https://github.com/vaskoz/dailycodingproblem-go/issues/204)
 * [Day 99](https://github.com/vaskoz/dailycodingproblem-go/issues/205)

day98/problem.go

@@ -0,0 +1,100 @@
+package day98
+
+// Board is a 2D grid of characters.
+type Board [][]rune
+
+// Position represents a Row and Col position
+// on the 2D board.
+type Position struct {
+	Row, Col int
+}
+
+// DoesExistSeqAdj returns true if the word exists sequentially in
+// adjacent cells. Cells can not be reused to achieve this goal.
+// Returns false otherwise.
+func DoesExistSeqAdj(board Board, word string) bool {
+	letters := []rune(word)
+	exists := false
+	for row := range board {
+		for col := range board[row] {
+			exists = exists || search(board, row, col, letters, make(map[Position]struct{}))
+			if exists {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+func search(board Board, row, col int, letters []rune, used map[Position]struct{}) bool {
+	if len(letters) == 0 {
+		return true
+	}
+	if board[row][col] != letters[0] {
+		return false
+	}
+	pos := Position{row, col}
+	if _, found := used[pos]; found {
+		return false
+	}
+	used[pos] = struct{}{}
+	// go up
+	if search(board, up(row, len(board)), col, letters[1:], used) {
+		return true
+	}
+	// go left
+	if search(board, row, left(col, len(board[0])), letters[1:], used) {
+		return true
+	}
+	// go right
+	if search(board, row, right(col, len(board[0])), letters[1:], used) {
+		return true
+	}
+	// go down
+	if search(board, down(row, len(board)), col, letters[1:], used) {
+		return true
+	}
+
+	delete(used, pos)
+	return false
+}
+
+func up(row, limit int) int {
+	var r int
+	if row == 0 {
+		r = limit - 1
+	} else {
+		r = row - 1
+	}
+	return r
+}
+
+func down(row, limit int) int {
+	var r int
+	if row == limit-1 {
+		r = 0
+	} else {
+		r = row + 1
+	}
+	return r
+}
+
+func left(col, limit int) int {
+	var c int
+	if col == 0 {
+		c = limit - 1
+	} else {
+		c = col - 1
+	}
+	return c
+}
+
+func right(col, limit int) int {
+	var c int
+	if col == limit-1 {
+		c = 0
+	} else {
+		c = col + 1
+	}
+	return c
+}

day98/problem_test.go

@@ -0,0 +1,57 @@
+package day98
+
+import "testing"
+
+var testcases = []struct {
+	board    Board
+	word     string
+	expected bool
+}{
+	{Board{
+		[]rune("ABCE"),
+		[]rune("SFCS"),
+		[]rune("ADEE"),
+	}, "ABCCED", true},
+	{Board{
+		[]rune("ABCE"),
+		[]rune("SFCS"),
+		[]rune("ADEE"),
+	}, "SEE", true},
+	{Board{
+		[]rune("ABCE"),
+		[]rune("SFCS"),
+		[]rune("ADEE"),
+	}, "ABCB", false},
+	{Board{
+		[]rune("ABCE"),
+		[]rune("SFCS"),
+		[]rune("ADEE"),
+	}, "ABCESCFSADEE", true},
+	{Board{
+		[]rune("ABCE"),
+		[]rune("SFCS"),
+		[]rune("ADEE"),
+	}, "ABCESCFSADEEA", false},
+	{Board{
+		[]rune("ABCE"),
+		[]rune("SFCS"),
+		[]rune("ADEE"),
+	}, "BCEA", true},
+}
+
+func TestDoesExistSeqAdj(t *testing.T) {
+	t.Parallel()
+	for tcid, tc := range testcases {
+		if result := DoesExistSeqAdj(tc.board, tc.word); result != tc.expected {
+			t.Errorf("TC%d expected %v got %v", tcid, tc.expected, result)
+		}
+	}
+}
+
+func BenchmarkDoesExistSeqAdj(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			DoesExistSeqAdj(tc.board, tc.word)
+		}
+	}
+}