題目:
給定一組整數array,印出所有的排列組合
EX: input: [1,2], output: [1,2], [2,1]
input: [1,2,3], output: [1,2,3],[1,3,2], [2,1,3], [2,3,1], [3,1,2], [3,2,1]
func helper(_ arr: inout [Int], _ index: Int) {
for i in index ..< arr.count {
arr.swapAt(index, i)
helper(&arr, index + 1)
arr.swapAt(index, i)
}
if index == arr.count {
print(arr)
}
}
var arr = [1,2,3,4]
helper(&arr,0)