[Swift]LeetCode1093. 大樣本統計 | Statistics from a Large Sample

時間 2019-11-11

標籤 swift leetcode1093 leetcode 樣本統計 statistics large sample 欄目 Swift 简体版

原文原文鏈接

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We sampled integers between 0 and 255, and stored the results in an array count: count[k] is the number of integers we sampled equal to k.github

Return the minimum, maximum, mean, median, and mode of the sample respectively, as an array of floating point numbers. The mode is guaranteed to be unique.數組

(Recall that the median of a sample is:微信

The middle element, if the elements of the sample were sorted and the number of elements is odd;
The average of the middle two elements, if the elements of the sample were sorted and the number of elements is even.)

Example 1:app

Input: count = [0,1,3,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
Output: [1.00000,3.00000,2.37500,2.50000,3.00000]

Example 2:spa

Input: count = [0,4,3,2,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
Output: [1.00000,4.00000,2.18182,2.00000,1.00000]

Constraints:code

count.length == 256
1 <= sum(count) <= 10^9
The mode of the sample that count represents is unique.
Answers within 10^-5 of the true value will be accepted as correct.

咱們對 0 到 255 之間的整數進行採樣，並將結果存儲在數組 count 中：count[k] 意味着採樣的整數爲 k。htm

咱們以浮點數數組的形式，分別返回樣本的最小值、最大值、平均值、中位數和衆數。其中，衆數是保證惟一的。blog

咱們先來回顧一下中位數的知識：

若是樣本中的元素有序，而且元素數量爲奇數時，中位數爲最中間的那個元素；
若是樣本中的元素有序，而且元素數量爲偶數時，中位數爲中間的兩個元素的平均值。

示例 1：

輸入：count = [0,1,3,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
輸出：[1.00000,3.00000,2.37500,2.50000,3.00000]

示例 2：

輸入：count = [0,4,3,2,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
輸出：[1.00000,4.00000,2.18182,2.00000,1.00000]

提示：

count.length == 256
1 <= sum(count) <= 10^9
計數表示的衆數是惟一的
答案與真實值偏差在 10^-5 之內就會被視爲正確答案

20ms

 1 class Solution {
 2     func sampleStats(_ count: [Int]) -> [Double] {
 3         guard count.count == 256 else { 
 4             assert(1 == 0, "Input error") 
 5         }
 6         var result = [Double]()
 7         var left = 0
 8         var right = 255
 9         while left <= 255 && count[left] == 0 {
10             left += 1
11         }
12         
13         while right > left && count[right] == 0 {
14             right -= 1
15         }
16         
17         result.append(Double(left))
18         result.append(Double(right))
19         
20         var counter = 0
21         var sum = 0
22         var mode = 0
23         var modeCounter = 0
24         for i in count.indices {
25             if count[i] > modeCounter {
26                 modeCounter = count[i]
27                 mode = i
28             }
29             counter += count[i]
30             sum += i * count[i]
31         }
32         result.append(Double(sum) / Double(counter))
33         
34         var start = counter % 2 != 0 ? counter / 2 + 1 : counter / 2
35         for i in 0..<count.count {
36             if start - count[i] > 0 {
37                 // print(start)
38                 // print(i)
39                 start -= count[i]
40                 continue
41             }
42             
43             if counter % 2 != 0 {
44                 result.append(Double(i))
45                 break
46             } else {
47                 if start - count[i] == 0 {
48                     var curr = i + 1
49                     
50                     while curr <= 255 && count[curr] == 0 {
51                         curr += 1
52                     } 
53                     result.append(Double(curr + i) / Double(2))
54                     break
55                 } else if start - count[i] < 0 {
56                     result.append(Double(i))
57                     break
58                 } 
59             }
60         }
61 
62         result.append(Double(mode))
63         return result
64     }
65 }

Runtime: 24 ms

Memory Usage: 21.2 MB

 1 class Solution {
 2     func sampleStats(_ count: [Int]) -> [Double] {
 3         var L:Int = 0
 4         var R:Int = 255
 5         while(L < 256 && count[L] == 0)
 6         {
 7             L += 1
 8         }
 9         while(L >= 0 && count[R] == 0)
10         {
11             R -= 1
12         }
13         let n:Int = count.reduce(0,+)
14         var sum:Double = 0
15         for i in 0...255
16         {
17             sum += Double(i * count[i])
18         }
19         let ave:Double = sum / Double(n)
20         var cur:Int = 0
21         var mid:Double = 0
22         if (n & 1) != 0
23         {
24             cur = 0
25             for i in 0...255
26             {
27                 cur += count[i]
28                 if cur >= (n + 1) / 2
29                 {
30                     mid = Double(i)
31                     break
32                 }
33             }
34         }
35         else
36         {
37             let x:Int = n / 2
38             let y:Int = x + 1
39             cur = 0
40             for i in 0...255
41             {
42                 cur += count[i]
43                 if cur >= x
44                 {
45                     mid += Double(i)
46                     break
47                 }
48             }
49             cur = 0
50             for i in 0...255
51             {
52                 cur += count[i]
53                 if cur >= y
54                 {
55                     mid += Double(i)
56                     break
57                 }
58             }
59             mid /= 2
60         }
61         let max_freq:Int = count.max() ?? Int.max
62         var mode:Double = -1.0
63         for i in 0...255
64         {
65             if count[i] == max_freq
66             {
67                 mode = Double(i)
68             }
69         }
70         return [Double(L), Double(R), ave, mid, mode]
71     }
72 }

36ms

 1 class Solution {
 2   func sampleStats(_ count: [Int]) -> [Double] {
 3     var minN = Int.max
 4     var maxN = Int.min
 5     var median: Double = 0
 6     var mode = 0
 7     var modeVal = 0
 8     var countOfNum = 0
 9     var sumVal = 0
10     for pair in count.enumerated() {
11       if pair.element != 0 {
12         minN = min(minN, pair.offset)
13         maxN = max(maxN, pair.offset)
14         if pair.element > mode {
15           mode = pair.element
16           modeVal = pair.offset
17         }
18         sumVal += pair.offset * pair.element
19         countOfNum += pair.element
20       }
21     }
22     
23     if countOfNum % 2 == 1 {
24       median = Double(valueBy(index: countOfNum/2, a: count))
25     } else {
26       median = Double(valueBy(index: countOfNum/2, a: count) + valueBy(index: countOfNum/2 - 1, a: count))/2
27     }
28     
29     return [Double(minN), Double(maxN), Double(sumVal)/Double(countOfNum), median, Double(modeVal)]
30   }
31   
32   func valueBy(index: Int, a: [Int]) -> Int {
33     var curentIndex = 0
34     for pair in a.enumerated() {
35       curentIndex += pair.element
36       if curentIndex > index {
37         return pair.offset
38       }
39     }
40     fatalError()
41   }
42 }

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