import Foundation
// Multiply rows of A by columns of B.
typealias Matrix = [[Int]]
// Print a 2D array (matrix)
func printMatrix(_ arr2d: Matrix) {
for row in arr2d {
for value in row {
// "%4d" formatting equivalent in Swift
let formatted = String(format: "%4d", value)
print(formatted, terminator: "")
}
print()
}
}
// Multiply matrices A and B into C
func multipleMatrix(a: Matrix, b: Matrix, c: inout Matrix) {
for i in 0..<c.count {
for j in 0..<c[i].count {
for k in 0..<a[i].count {
c[i][j] += a[i][k] * b[k][j]
}
}
}
}
func main() {
// Create matrices
let a: Matrix = [
[1, 8, 5],
[6, 7, 1],
[8, 7, 6]
]
let b: Matrix = [
[4, 8, 1],
[6, 5, 3],
[4, 6, 5]
]
// Initialize result matrix C with zeros
var c: Matrix = Array(
repeating: Array(repeating: 0, count: b[0].count),
count: a.count
)
// c[0][0] = (a[0][0] * b[0][0]) + (a[0][1] * b[1][0]) + (a[0][2] * b[2][0])
printMatrix(a)
print()
printMatrix(b)
print()
multipleMatrix(a: a, b: b, c: &c)
printMatrix(c)
}
main()
/*
run:
1 8 5
6 7 1
8 7 6
4 8 1
6 5 3
4 6 5
72 78 50
70 89 32
98 135 59
*/
