[Swift]LeetCode859. 亲密字符串 | Buddy Strings

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Given two strings A and B of lowercase letters, return true if and only if we can swap two letters in A so that the result equals B.

Example 1:

Input: A = "ab", B = "ba"
Output: true

Example 2:

Input: A = "ab", B = "ab"
Output: false

Example 3:

Input: A = "aa", B = "aa"
Output: true

Example 4:

Input: A = "aaaaaaabc", B = "aaaaaaacb"
Output: true

Example 5:

Input: A = "", B = "aa"
Output: false

Note:

1. 0 <= A.length <= 20000
2. 0 <= B.length <= 20000
3. A and B consist only of lowercase letters.

---

给定两个由小写字母构成的字符串 A 和 B ，只要我们可以通过交换 A 中的两个字母得到与 B 相等的结果，就返回 true ；否则返回 false 。

示例 1：

输入： A = "ab", B = "ba"
输出： true

示例 2：

输入： A = "ab", B = "ab"
输出： false

示例 3:

输入： A = "aa", B = "aa"
输出： true

示例 4：

输入： A = "aaaaaaabc", B = "aaaaaaacb"
输出： true

示例 5：

输入： A = "", B = "aa"
输出： false

提示：

1. 0 <= A.length <= 20000
2. 0 <= B.length <= 20000
3. A 和 B 仅由小写字母构成。

---

16ms

class Solution {
    func buddyStrings(_ A: String, _ B: String) -> Bool {
        guard !A.isEmpty,!B.isEmpty, A.count == B.count else {
            return false
        }
        if A == B && Set(A).count < A.count { return true }
        let arrayA = Array(A)
        let arrayB = Array(B)
        var diffIndexArray:Array<Int> = []
        for i in 0..<A.count {
            if arrayA[i] != arrayB[i] {
                diffIndexArray.append(i)
            }
            if diffIndexArray.count > 2 {
                return false
            }
        }
        if diffIndexArray.count != 2 { return false }   
        return arrayA[diffIndexArray[1]] == arrayB[diffIndexArray[0]] && arrayA[diffIndexArray[0]] == arrayB[diffIndexArray[1]]
    }
}

---

20ms

class Solution {
    func buddyStrings(_ As: String, _ Bs: String) -> Bool {    
    guard As.count == Bs.count && As.count > 1 else {
        return false
    }    
    if As == Bs {
        if Set(As).count < As.count {
            return true
        }        
        return false
    }    
    let A = Array(As)
    let B = Array(Bs)
    var diff = [Int]()
    for i in 0..<A.count {
        if A[i] != B[i] {
            diff.append(i)
        }        
        if diff.count > 2 {
            return false
        }
    }    
    guard diff.count == 2 else {
        return false
    }    
    if  A[diff[0]] == B[diff[1]] && A[diff[1]] == B[diff[0]]  {
        return true
    }    
    return false
    }
}

---

24ms

class Solution {
    func buddyStrings(_ A: String, _ B: String) -> Bool {
        if A.length != B.length { return false }
        if A.count < 2 || A.count != B.count {
            return false
        }
        if A == B && Set(A).count < A.count {
            return true
        }
        
        var a = Array(A)
        var b = Array(B)
        var array = [String]()
        
        if A != B {
            for i in 0 ..< a.count {
                if a[i] != b[i] {
                    array.append(String(a[i]))
                    array.append(String(b[i]))
                }
            }
            if array.reversed() == array {
                return true
            }
        }
        return false
    }
}

---

28ms

class Solution {
    func buddyStrings(_ A: String, _ B: String) -> Bool {
        if A.count != B.count {
            return false
        }  
        var map = [Character: Int]()
        var x = -1
        var y = -1
        let arrayA = Array(A)
        let arrayB = Array(B)   
        for i in 0..<A.count {
            map[arrayA[i], default: 0] += 1           
            if arrayA[i] == arrayB[i] {
                continue
            }
            if x == -1 {
                x = i
            }
            else if y == -1 {
                y = i
            }
            else {
                return false
            }
        }
        if x != -1 && y != -1 {
            if arrayA[x] == arrayB[y] && arrayA[y] == arrayB[x] {
                return true
            }
        }
        else {
            for (_, value) in map {
                if value > 1 {
                    return true
                }
            }
        }
        return false
    }
}

---

32ms

class Solution {
    func buddyStrings(_ A: String, _ B: String) -> Bool {
        if A.length != B.length { return false }
        if A.count < 2 || A.count != B.count {
            return false
        }
        if A == B && Set(A).count < A.count {
            return true
        }
        
        var a = Array(A).map({ String($0) })
        var b = Array(B).map({ String($0) })
        var arr = [String]()
        
        if A != B {
            for i in 0 ..< a.count {
                if a[i] != b[i] {
                    arr.append(a[i])
                    arr.append(b[i])
                }
            }
            if arr.reversed() == arr { return true }
        }
        
        return false
    }
}

---

40ms

class Solution {
    func buddyStrings(_ A: String, _ B: String) -> Bool {
        guard A.count == B.count else {
            return false
        }
        var diff = [(Character, Character)]()

        for (a, b) in zip(A, B) {
            if a != b {
                diff.append((a, b))
                if diff.count > 2 {
                    return false
                }
            }
        }

        return (diff.count == 0 && Set(Array(A)).count < A.count) ||
                (diff.count == 2 && diff[0] == (diff[1].1, diff[1].0))
    }
}