Swift - 搜索數組中的數字模式

Question

我在Swift中整理了一個算法，其中一部分需要檢查給定的數組並確定是否有2（或3,4個註釋掉）數字的序列是重複。我的源代碼是來自Java的代碼塊，爲了我最好的理解，我試圖將它轉換爲Swift - Playgrounds。它有點工作，但其上運行的代碼

後引發錯誤「無法UPPERBOUND <形成範圍下界」

崩潰之前，輸出是正確的，並提供了模式的序列。請問這怎麼能防止？

let array1 = [12, 4, 5, 7, 1, 2] 
let array2 = [1, 2, 3, 1, 2, 3, 1, 2, 3] 
let array3 = [1, 1, 1, 1, 1, 1 ] 
let array4 = [1, 2, 4, 12, 13, 1, 8, 4, 12, 4 ] 
let array5 = [17,39,78,324,43,33,234,99,34,555,39,78,324,43,45,92 ] 

func hasPattern(c:Array<Int>) { 
for i in 0..<c.count { 
    var jj = i + 1 

    let step2 = (c.count - i) 
    for j in jj..<step2 { 

     if(c[j] == c[i]){ 

      // pattern of 4 numbers repeating 
      /*if(c[j+1] == c[i+1] && c[j+2] == c[i+2] && c[j+3] == c[i+3]){ 
       print("\(c[i]), \(c[i+1]), \(c[i+2]), \(c[i+3])")      
      }*/ 

      // pattern of 3 numbers repeating 
      /* 
      if(c[j+1] == c[i+1] && c[j+2] == c[i+2]){ 
      print("\(c[i]), \(c[i+1]), \(c[i+2])") 
      } 
      */ 

      // pattern of 2 numbers repeating 
      if(c[j+1] == c[i+1]){ 
       print("\(c[i]), \(c[i+1])") 
      } 
     } 
     } 
    } 
} 
/* 
print(hasPattern(c: array1)) 
print(hasPattern(c: array2)) 
print(hasPattern(c: array3))*/ 
//print(hasPattern(c: array4)) 

print(hasPattern(c: array5)) 

我在這裏錯過了什麼？謝謝。

Answer 1

我還是覺得你的問題不完全清楚。數組是否有2個重複子序列[2,3,2]，即使它們共享一個元素？

如果你想避免「無法形成範圍...」的錯誤，使用stride：

// A more convenient way to check if two arrays are equal 
func ==(lhs: [Int], rhs: [Int]) -> Bool { 
    guard lhs.count == rhs.count else { return false } 

    for (l, r) in zip(lhs, rhs) { 
     if l != r { return false } 
    } 
    return true 
} 

// If there's no matching pattern, this function will return nil 
// instead of an aempty array. Change it if you want to 
func hasPattern(array: [Int], length: Int) -> [[Int]]? { 
    guard array.count >= length * 2 else { return nil } 

    var result = [[Int]]() 
    for i in 0..<(array.count - length) { 
     let subarray1 = array[i..<(i+length)] 

     for j in stride(from: i+1, to: array.count - length, by: 1) { 
      let subarray2 = array[j..<(j+length)] 
      if subarray1 == subarray2 { 
       result.append(Array(subarray1)) 
      } 
     } 
    } 
    return result.isEmpty ? nil : result 
} 

if let patterns = hasPattern(array: array5, length: 3) { 
    print(patterns) // [[39, 78, 324], [78, 324, 43]] 
} else { 
    print("No repeating pattern found") 
} 

Answer 2

你的問題在於你的內在循環。對於數組可以說，大小爲5，環如下：

for i in 0..<5 
    for j in i+1..<5-i 

有會來一個點，那+i和-i碰撞和您的下界變得比你的上限更大。

如果你不明確需要推出自己的algoritm，最好是使用進行搜索：

func hasPattern(elements :Array<Int>) -> Bool { 
    var index = 0 
    while index < (array.count - elements.count) { 
     let subarray = array[index ..< (index + elements.count)] 
     if subarray.elementsEqual(elements) { 
      return true 
     } 
     index += 1 
    } 
    return false 
} 

哪裏array是你在搜索陣列