Merge pull request #859 from vaskoz/day425

Day425

README.md

@@ -421,4 +421,5 @@ problems from
 * [Day 422](https://github.com/vaskoz/dailycodingproblem-go/issues/852)
 * [Day 423](https://github.com/vaskoz/dailycodingproblem-go/issues/854)
 * [Day 424](https://github.com/vaskoz/dailycodingproblem-go/issues/856)
+* [Day 425](https://github.com/vaskoz/dailycodingproblem-go/issues/858)
 

day425/problem.go

@@ -0,0 +1,146 @@
+package day425
+
+// Chessboard is a slice of strings. The first string represents the top row
+// and the last string represents the bottom row of the board.
+// The top is the black player's side and the bottom is the white player's side.
+type Chessboard []string
+
+// IsSoloBlackKingInCheck answers if a solo black king is in check.
+// All other pieces on the board are white pieces.
+func IsSoloBlackKingInCheck(board Chessboard) bool {
+	kR, kC := findBlackKing(board)
+
+	for r := range board {
+		for c := range board[r] {
+			switch board[r][c] {
+			case 'B':
+				if bishop(board, r, c, kR, kC) {
+					return true
+				}
+			case 'N':
+				if knight(board, r, c, kR, kC) {
+					return true
+				}
+			case 'P':
+				if pawn(board, r, c, kR, kC) {
+					return true
+				}
+			case 'R':
+				if rook(board, r, c, kR, kC) {
+					return true
+				}
+			case 'Q':
+				if queen(board, r, c, kR, kC) {
+					return true
+				}
+			}
+		}
+	}
+
+	return false
+}
+
+func knight(_ Chessboard, nR, nC, kR, kC int) bool {
+	return (nR-2 == kR && nC+1 == kC) ||
+		(nR-1 == kR && nC+2 == kC) ||
+		(nR+1 == kR && nC+2 == kC) ||
+		(nR+2 == kR && nC+1 == kC) ||
+		(nR+2 == kR && nC-1 == kC) ||
+		(nR+1 == kR && nC-2 == kC) ||
+		(nR-1 == kR && nC-2 == kC) ||
+		(nR-2 == kR && nC-1 == kC)
+}
+
+func pawn(_ Chessboard, pR, pC, kR, kC int) bool {
+	return (pR-1 == kR && pC-1 == kC) || (pR-1 == kR && pC+1 == kC)
+}
+
+func queen(board Chessboard, qR, qC, kR, kC int) bool {
+	return rook(board, qR, qC, kR, kC) || bishop(board, qR, qC, kR, kC)
+}
+
+func rook(board Chessboard, rR, rC, kR, kC int) bool {
+	// up
+	for r := rR - 1; r >= 0; r-- {
+		if r == kR && rC == kC {
+			return true
+		} else if board[r][rC] != '.' {
+			break
+		}
+	}
+	// left
+	for c := rC - 1; c >= 0; c-- {
+		if rR == kR && c == kC {
+			return true
+		} else if board[rR][c] != '.' {
+			break
+		}
+	}
+	// right
+	for c := rC + 1; c < 8; c++ {
+		if rR == kR && c == kC {
+			return true
+		} else if board[rR][c] != '.' {
+			break
+		}
+	}
+	// down
+	for r := rR + 1; r < 8; r++ {
+		if r == kR && rC == kC {
+			return true
+		} else if board[r][rC] != '.' {
+			break
+		}
+	}
+
+	return false
+}
+
+func bishop(board Chessboard, bR, bC, kR, kC int) bool {
+	// up-right
+	for r, c := bR-1, bC+1; r >= 0 && c < 8; r, c = r-1, c+1 {
+		if r == kR && c == kC {
+			return true
+		} else if board[r][c] != '.' {
+			break
+		}
+	}
+	// up-left
+	for r, c := bR-1, bC-1; r >= 0 && c >= 0; r, c = r-1, c-1 {
+		if r == kR && c == kC {
+			return true
+		} else if board[r][c] != '.' {
+			break
+		}
+	}
+	// down-right
+	for r, c := bR+1, bC+1; r < 8 && c < 8; r, c = r+1, c+1 {
+		if r == kR && c == kC {
+			return true
+		} else if board[r][c] != '.' {
+			break
+		}
+	}
+	// down-left
+	for r, c := bR+1, bC-1; r < 8 && c >= 0; r, c = r+1, c-1 {
+		if r == kR && c == kC {
+			return true
+		} else if board[r][c] != '.' {
+			break
+		}
+	}
+
+	return false
+}
+
+func findBlackKing(board Chessboard) (row int, col int) {
+	for row := range board {
+		for col := range board[row] {
+			if board[row][col] == 'K' {
+				return row, col
+			}
+		}
+	}
+
+	return
+}

day425/problem_test.go

@@ -0,0 +1,184 @@
+package day425
+
+import "testing"
+
+// nolint
+var testcases = []struct {
+	board   Chessboard
+	inCheck bool
+}{
+	{
+		Chessboard{
+			"...K....",
+			"........",
+			".B......",
+			"......P.",
+			".......R",
+			"..N.....",
+			"........",
+			".....Q..",
+		},
+		true,
+	},
+	{
+		Chessboard{
+			"...K....",
+			"........",
+			".P..N...",
+			"......P.",
+			".......R",
+			"..N.....",
+			"........",
+			".....Q..",
+		},
+		true,
+	},
+	{
+		Chessboard{
+			"...K....",
+			"..P.....",
+			".P..N...",
+			"......P.",
+			".......R",
+			"..N.....",
+			"........",
+			".....Q..",
+		},
+		true,
+	},
+	{
+		Chessboard{
+			"...K....",
+			"........",
+			".P......",
+			"......P.",
+			".......R",
+			"..N.....",
+			"........",
+			"...R.Q..",
+		},
+		true,
+	},
+	{
+		Chessboard{
+			"K.......",
+			"........",
+			".P......",
+			"......P.",
+			".......R",
+			"..N.....",
+			"........",
+			"...R...Q",
+		},
+		true,
+	},
+	{
+		Chessboard{
+			"Q.......",
+			"........",
+			".PK.....",
+			"......P.",
+			".......R",
+			"..N.....",
+			"........",
+			"...R....",
+		},
+		true,
+	},
+	{
+		Chessboard{
+			"....Q...",
+			"........",
+			".PK.....",
+			"......P.",
+			".......R",
+			"..N.....",
+			"........",
+			"...R....",
+		},
+		true,
+	},
+	{
+		Chessboard{
+			"........",
+			"........",
+			".PK...R.",
+			"......P.",
+			".......R",
+			"..N.....",
+			"........",
+			"........",
+		},
+		true,
+	},
+	{
+		Chessboard{
+			"........",
+			"........",
+			"Q.K.....",
+			"......P.",
+			".......R",
+			"..N.....",
+			"........",
+			"........",
+		},
+		true,
+	},
+	{
+		Chessboard{
+			"..R.....",
+			"........",
+			"..K.....",
+			"......P.",
+			".......R",
+			"..N.....",
+			"........",
+			"........",
+		},
+		true,
+	},
+	{
+		Chessboard{
+			"...K....",
+			"........",
+			"........",
+			"PPPPPPPP",
+			".B.....R",
+			"P.N.....",
+			"....Q...",
+			".R......",
+		},
+		false,
+	},
+	{ // missing king
+		Chessboard{
+			"........",
+			"........",
+			"........",
+			"PPPPPPPP",
+			".B.....R",
+			"P.N.....",
+			"....Q...",
+			".R......",
+		},
+		false,
+	},
+}
+
+func TestIsSoloBlackKingInCheck(t *testing.T) {
+	t.Parallel()
+
+	for tcid, tc := range testcases {
+		if result := IsSoloBlackKingInCheck(tc.board); result != tc.inCheck {
+			t.Errorf("testcase id:%d expected %v, got %v", tcid, tc.inCheck, result)
+		}
+	}
+}
+
+func BenchmarkIsSoloBlackKingInCheck(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			IsSoloBlackKingInCheck(tc.board)
+		}
+	}
+}