Solution for play fair cipher

go/solution.go

@@ -1 +1,117 @@
 package main
+
+import (
+	"fmt"
+	"strings"
+)
+
+// Matrix creates a 5x5 matrix for the Playfair cipher
+func Matrix(chavi string) [5][5]rune {
+	chavi = strings.ToUpper(chavi)
+	used := make(map[rune]bool)
+	var matrix [5][5]rune
+	row, col := 0, 0
+
+	// Add key characters to the matrix
+	for _, char := range chavi {
+		if char == 'J' {
+			char = 'I'
+		}
+		if !used[char] {
+			matrix[row][col] = char
+			used[char] = true
+			col++
+			if col == 5 {
+				col = 0
+				row++
+			}
+		}
+	}
+
+	// Add remaining characters to the matrix
+	for char := 'A'; char <= 'Z'; char++ {
+		if char == 'J' {
+			continue
+		}
+		if !used[char] {
+			matrix[row][col] = char
+			used[char] = true
+			col++
+			if col == 5 {
+				col = 0
+				row++
+			}
+		}
+	}
+	return matrix
+}
+
+// FindPosition finds the row and column of a character in the matrix
+func PositionLookUp(matrix [5][5]rune, char rune) (int, int) {
+	if char == 'J' {
+		char = 'I'
+	}
+	// Find the character in the matrix and return its position	
+	for row := range matrix {
+		for col := range matrix[row] {
+			if matrix[row][col] == char {
+				return row, col
+			}
+		}
+	}
+	return -1, -1
+}
+
+// DecryptPair decrypts a pair of characters using the Playfair cipher
+func EncodePair(matrix [5][5]rune, char1, char2 rune) (rune, rune) {
+	row1, col1 := PositionLookUp(matrix, char1)
+	row2, col2 := PositionLookUp(matrix, char2)
+
+	if row1 == row2 {
+		col1 = (col1 + 4) % 5
+		col2 = (col2 + 4) % 5
+	} else if col1 == col2 {
+		row1 = (row1 + 4) % 5
+		row2 = (row2 + 4) % 5
+	} else {
+		col1, col2 = col2, col1
+	}
+
+	return matrix[row1][col1], matrix[row2][col2]
+}
+
+// DecryptPlayfair decrypts a message using the Playfair cipher
+func decodePlayfair(matrix [5][5]rune, message string) string {
+	message = strings.ToUpper(message)
+	message = strings.ReplaceAll(message, " ", "")
+	var decrypted []rune
+	// Process pairs of characters in the message
+	for i := 0; i < len(message); i += 2 {
+		char1 := rune(message[i])
+		char2 := rune(message[i+1])
+
+		if char1 == 'X' {
+			char1 = 'X'
+		}
+		if char2 == 'X' {
+			char2 = 'X'
+		}
+
+		decryptedChar1, decryptedChar2 := EncodePair(matrix, char1, char2)
+		decrypted = append(decrypted, decryptedChar1, decryptedChar2)
+	}
+
+	return string(decrypted)
+}
+
+func main() {
+	key := "SUPERSPY"
+	message := "IKEWENENXLNQLPZSLERUMRHEERYBOFNEINCHCV"
+
+	matrix := Matrix(key)
+	decryptedMessage := decodePlayfair(matrix, message)
+
+	// Remove 'X' and output the result
+	decryptedMessage = strings.ReplaceAll(decryptedMessage,"X", "")
+	fmt.Println(decryptedMessage)
+}