add new solutions

solutions/0/q79/solution.go

@@ -0,0 +1,61 @@
+package q79
+
+func search(board [][]byte, word string, prefixLen, row, col int) bool {
+	if row < 0 || col < 0 || row >= len(board) || col >= len(board[0]) {
+		return false
+	}
+	if word[prefixLen] != board[row][col] {
+		return false
+	}
+	if prefixLen+1 == len(word) {
+		return true
+	}
+
+	c := board[row][col]
+	board[row][col] = '#'
+	yes := false ||
+		search(board, word, prefixLen+1, row, col+1) ||
+		search(board, word, prefixLen+1, row, col-1) ||
+		search(board, word, prefixLen+1, row+1, col) ||
+		search(board, word, prefixLen+1, row-1, col)
+
+	board[row][col] = c
+	return yes
+}
+
+func exist(board [][]byte, word string) bool {
+	w, h := len(board[0]), len(board)
+	if len(word) > w*h {
+		return false
+	}
+	charFreq := make([]int, 26*2)
+	idx := func(b byte) byte {
+		if b >= 'a' {
+			return b - 'a' + 26
+		}
+		return b - 'A'
+	}
+	for row := range board {
+		for col := range board[0] {
+			charFreq[idx(board[row][col])]++
+		}
+	}
+	for i := range len(word) {
+		ii := idx(word[i])
+		charFreq[ii]--
+		if charFreq[ii] < 0 {
+			return false
+		}
+	}
+
+	for row := range board {
+		for col := range board[0] {
+			if search(board, word, 0, row, col) {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+var _ = exist