[Swift]LeetCode888. 公平的糖果交換 | Fair Candy Swap

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➤微信公衆號：山青詠芝（shanqingyongzhi）
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Alice and Bob have candy bars of different sizes: A[i] is the size of the i-th bar of candy that Alice has, and B[j] is the size of the j-th bar of candy that Bob has.

Since they are friends, they would like to exchange one candy bar each so that after the exchange, they both have the same total amount of candy.  (The total amount of candy a person has is the sum of the sizes of candy bars they have.)

Return an integer array ans where ans[0] is the size of the candy bar that Alice must exchange, and ans[1] is the size of the candy bar that Bob must exchange.

If there are multiple answers, you may return any one of them.  It is guaranteed an answer exists. 

Example 1:

Input: A = [1,1], B = [2,2] Output: [1,2] 

Example 2:

Input: A = [1,2], B = [2,3] Output: [1,2] 

Example 3:

Input: A = [2], B = [1,3] Output: [2,3] 

Example 4:

Input: A = [1,2,5], B = [2,4] Output: [5,4] 

Note:

• 1 <= A.length <= 10000
• 1 <= B.length <= 10000
• 1 <= A[i] <= 100000
• 1 <= B[i] <= 100000
• It is guaranteed that Alice and Bob have different total amounts of candy.
• It is guaranteed there exists an answer.

---

愛麗絲和鮑勃有不一樣大小的糖果棒：A[i] 是愛麗絲擁有的第 i 塊糖的大小，B[j] 是鮑勃擁有的第 j 塊糖的大小。

由於他們是朋友，因此他們想交換一個糖果棒，這樣交換後，他們都有相同的糖果總量。（一我的擁有的糖果總量是他們擁有的糖果棒大小的總和。）

返回一個整數數組 ans，其中 ans[0] 是愛麗絲必須交換的糖果棒的大小，ans[1] 是 Bob 必須交換的糖果棒的大小。

若是有多個答案，你能夠返回其中任何一個。保證答案存在。 

示例 1：

輸入：A = [1,1], B = [2,2]
輸出：[1,2]

示例 2：

輸入：A = [1,2], B = [2,3]
輸出：[1,2]

示例 3：

輸入：A = [2], B = [1,3]
輸出：[2,3]

示例 4：

輸入：A = [1,2,5], B = [2,4]
輸出：[5,4] 

提示：

• 1 <= A.length <= 10000
• 1 <= B.length <= 10000
• 1 <= A[i] <= 100000
• 1 <= B[i] <= 100000
• 保證愛麗絲與鮑勃的糖果總量不一樣。
• 答案確定存在。

---

500ms

 

 1 class Solution {
 2     func fairCandySwap(_ A: [Int], _ B: [Int]) -> [Int] {
 3         var diff = 0
 4         var i = 0
 5         var j = 0
 6         while i < A.count || j < B.count {
 7             if i < A.count {
 8                 diff -= A[i]
 9                 i += 1
10             }
11             
12             if j < B.count {
13                 diff += B[j]
14                 j += 1
15             }
16         }
17         
18         i = 0
19         j = 0
20         diff /= 2        
21         var bSet = Set<Int>()
22         for b in B {
23             bSet.insert(b)
24         }
25         
26         for a in A {
27             let pairedValue = a + diff
28             if bSet.contains(pairedValue) {
29                 return [a, pairedValue]
30             }
31         }
32         
33         return []
34     }
35 }

---

504ms

 1 class Solution {
 2     func fairCandySwap(_ A: [Int], _ B: [Int]) -> [Int] {
 3         let aSum = A.reduce(0) { $0 + $1 }
 4         let bSum = B.reduce(0) { $0 + $1 }
 5         let difference = bSum - aSum
 6         let bSet = Set(B.map { $0 })
 7         for a in A {
 8             if bSet.contains(a +  difference / 2) {
 9                 return [a, a +  difference / 2]
10             }
11         }
12         return [-1, -1]
13     }
14 }

---

Runtime: 516 ms

Memory Usage: 19.1 MB

 1 class Solution {
 2     func fairCandySwap(_ A: [Int], _ B: [Int]) -> [Int] {
 3         var dif:Int = (A.reduce(0,+) - B.reduce(0,+)) / 2
 4         var S:Set<Int> = Set<Int>()
 5         for a in A
 6         {
 7             S.insert(a)
 8         }
 9         for b in B
10         {
11             if S.contains(b + dif)
12             {
13                 return [b + dif, b]
14             }
15         }
16         return []
17     }
18 }

---

552ms

 1 class Solution {
 2     func fairCandySwap(_ A: [Int], _ B: [Int]) -> [Int] {
 3         let sumA = A.reduce(0, +)
 4         let sumB = B.reduce(0, +)
 5         
 6         let setA = Set(A)
 7         let setB = Set(B)
 8         
 9         for item in setA{
10             let itemB = (sumB - sumA + 2 * item) / 2
11             if setB.contains(itemB){
12                 return [item, itemB]
13             }           
14         }
15 
16         return [0,0]
17     }
18 }

---

556ms

 1 class Solution {
 2     func fairCandySwap(_ A: [Int], _ B: [Int]) -> [Int] {
 3         let sumA = A.reduce(0, +)
 4         let sumB = B.reduce(0, +)
 5         let bSet = Set(B)
 6         for x in A {
 7             let y = x + (sumB - sumA) / 2
 8             if bSet.contains(y){
 9                 return [x,y]
10             }            
11         }
12         return []  
13     }
14 }

---

580ms

 1 class Solution {
 2     func fairCandySwap(_ A: [Int], _ B: [Int]) -> [Int] {
 3         var totalA = 0
 4         var totalB = 0
 5         var mark = [Int : Bool]()
 6         for a in A {
 7             totalA += a
 8             mark[a] = true
 9         }
10         for b in B {
11             totalB += b
12         }
13         
14         let dis = (totalB - totalA) / 2
15         for b in B {
16             if let _ = mark[b - dis] {
17                 return [b - dis, b]
18             }
19         }
20         return [Int]()
21     }
22 }