Swift 3 comparing array indexes

问题

If i have two arrays & i want to compare their indexes, for ex:

let var a1 = ["1", "2", "3"]
let var a2 = ["3", "2", "3"]

And i wanted to print something to say which index wasn't the same, such as:

if a1[0] != a2[0] && a1[1] == a2[1] && a1[2] == a2[2]{
print("Index 0 is not the same.")

Would i have to write 7 more of those statements to show all 8 possibilities of all correct/all wrong/index 1&1 wrong, etc?

Thank you!

回答1:

You can get all indexes like this:

let diffIndex = zip(a1, a2).enumerated().filter {$1.0 != $1.1}.map {$0.offset}

Explanation:

zip produces a sequence of pairs
enumerated() adds an index to the sequence
filter keeps only pairs with different values
map harvests the index, and builds the sequence of results.

Running this on

let a1 = ["1", "2", "3", "4"]
let a2 = ["3", "2", "3", "5"]

This produces a sequence [0, 3]

回答2:

Use a for loop:

for i in 0..<a1.length {
    if a1[i] != a2[i] {
        print("Index \(i) is not the same")
    }
}

Generally if you find yourself repeating the same code but with different numbers, you can substitute it with a for loop.

回答3:

Try this

let a1 = ["1", "2", "3"]
let a2 = ["3", "2", "3"]

let result = zip(a1, a2).map({ $0 == $1 }).reduce(true, {$0 && $1})

回答4:

Surely you could do something like this:

let a1 = ["1", "2", "3"]
let a2 = ["3", "2", "3"]

var compareResult : [String] = [String]()

if a1.count == a2.count { // Need to check they have same length

    for count in 0..<a1.count {
        let result : String = a1[count] == a2[count] ? "MATCH" : "MISMATCH"
        compareResult.append(result)
    }

    print(compareResult)
    // Do something more interesting with compare result...
}

来源：https://stackoverflow.com/questions/39987260/swift-3-comparing-array-indexes

标签

arrays

swift

indexing