[Swift]LeetCode506. 相对名次 | Relative Ranks

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Given scores of N athletes, find their relative ranks and the people with the top three highest scores, who will be awarded medals: "Gold Medal", "Silver Medal" and "Bronze Medal".

Example 1:

Input: [5, 4, 3, 2, 1]
Output: ["Gold Medal", "Silver Medal", "Bronze Medal", "4", "5"]
Explanation: The first three athletes got the top three highest scores, so they got "Gold Medal", "Silver Medal" and "Bronze Medal". 
For the left two athletes, you just need to output their relative ranks according to their scores.

 Note:

1. N is a positive integer and won't exceed 10,000.
2. All the scores of athletes are guaranteed to be unique.

---

 给出 N 名运动员的成绩，找出他们的相对名次并授予前三名对应的奖牌。前三名运动员将会被分别授予 “金牌”，“银牌” 和“ 铜牌”（"Gold Medal", "Silver Medal", "Bronze Medal"）。

(注：分数越高的选手，排名越靠前。)

示例 1:

输入: [5, 4, 3, 2, 1]
输出: ["Gold Medal", "Silver Medal", "Bronze Medal", "4", "5"]
解释: 前三名运动员的成绩为前三高的，因此将会分别被授予 “金牌”，“银牌”和“铜牌” ("Gold Medal", "Silver Medal" and "Bronze Medal").
余下的两名运动员，我们只需要通过他们的成绩计算将其相对名次即可。

提示:

1. N 是一个正整数并且不会超过 10000。
2. 所有运动员的成绩都不相同。

---

class Solution {
    func findRelativeRanks(_ nums: [Int]) -> [String] {
        var arr:[Int] = nums
        //降序排序
        arr = arr.sorted(by: >)
        let len:Int = nums.count
        var res:[String] = Array(repeating: "",count: len)

        //从nums中寻找与arr[j]相同元素,在res中对应位置赋值为j+1, j=0,1,2时特殊处理
        for i in 0..<len
        {
            for j in 0..<len
            {
                if nums[i] == arr[j]
                {
//整个switch语句在第一个匹配switch案例完成后立即完成其执行，而不需要显式break语句。  
//尽管break在Swift中不需要，但您可以使用break语句来匹配和忽略特定情况，
//或者在该情况完成执行之前中断匹配的情况。  
                    switch j
                    {
                        case 0:
                        res[i] = "Gold Medal"
                        case 1:
                        res[i] = "Silver Medal"
                        case 2:
                        res[i] = "Bronze Medal"           
                        default:
                        res[i] = String(j + 1)                        
                    }
                 break
                }              
            }
        }
        return res
    }
}

---

48ms

class Solution {
    func findRelativeRanks(_ nums: [Int]) -> [String] {
        guard nums.count > 0 else {
            return []
        }
        var index = [Int:Int]()
        for i in 0..<nums.count {
            index[nums[i]] = i
        }
        let sorted = nums.sorted(by: >)
        var rank = [String](repeating: "", count: nums.count)
        for i in 0..<sorted.count {
            if let idx = index[sorted[i]] {
                if i == 0 {
                    rank[idx] = "Gold Medal" 
                } else if i == 1 {
                    rank[idx] = "Silver Medal"
                } else if i == 2 {
                    rank[idx] = "Bronze Medal"
                } else {
                    rank[idx] = String(i+1)
                }
            }

        }
        return rank
    }
}

---

44ms

class Solution {
    func findRelativeRanks(_ nums: [Int]) -> [String] {
        let arr = nums.sorted(by: >)
        var res = [String]()
        var dict = [Int:String]()
        for i in 0..<arr.count {
            if i == 0 {
                dict[arr[i]] = "Gold Medal"
            } else if i == 1 {
                dict[arr[i]] = "Silver Medal"
            } else if i == 2 {
                dict[arr[i]] = "Bronze Medal"
            } else {
                dict[arr[i]] = "\(i+1)"
            }
        }
        for i in nums {
            res.append(dict[i]!)
        }
        return res
    }
}

---

80ms

class Solution {
    func findRelativeRanks(_ nums: [Int]) -> [String] {
        var nums2 = nums.sorted()
        return nums.map({ (num) -> String in
            var left = 0
            var right = nums.count - 1
            while left < right {
                let mid = left + (right - left) / 2
                let val = nums2[mid]
                if val > num {
                    right = mid
                } else if val < num {
                    left = mid + 1
                } else {
                    left = mid
                    break
                }
            }
            
            var string = ""
            if left == nums.count - 1 {
                string = "Gold Medal"
            } else if left == nums.count - 2 {
                string = "Silver Medal"
            } else if left == nums.count - 3 {
                string = "Bronze Medal"
            } else {
                string = String(nums.count - left)
            }
            return string
        })
    }
}

---

172ms

class Solution {
    func findRelativeRanks(_ nums: [Int]) -> [String] {
        let sortedNums = nums.sorted().reversed()
        var ranks = ["Gold Medal", "Silver Medal", "Bronze Medal"]
        ranks = nums.count > 3 ? ranks + (4..<nums.count+1).map{ return String($0) } : ranks
        let dict = Dictionary(uniqueKeysWithValues: zip(sortedNums, ranks))
        return nums.map{ return dict[$0]! }
    }
}