遞歸添加subet

Question

我有這樣的情況下，對於輸入的工作原理：

{-5,0,5}, 2, 0 // which correctly evaluates to true 
{-5,0,5}, 3, 4 // which correctly evaluates to false 
{-5,0,5}, 3, 0 // which correctly evaluates to true 

但隨着輸入：

{6,5,6}, 2, 12 // says false when true 

它不會給出正確的布爾值... 燦有人幫助調試問題？

public static boolean subset(int[] array, int n, int target) { 
    for (int i = 0; i < array.length; i++) { 
     int[] list = new int[array.length - 1]; 

     for (int j = 0; j < array.length - 1; j++) { 
      list[j] = array[j+1]; 
     } 
     subset(list, n, target); 
    } 

    int sum = 0; 
    for (int i = 0; i < array.length; i++) { 
     sum += array[i]; 
    } 

    if (sum == target) { 
     return true; 
    } 
    else { 
     return false; 
    } 
} 

Answer 1

不知道你在計算什麼，但我懷疑你的問題在於子集（list，n，target）的遞歸調用。你沒有改變一個對象，你忽略了返回值。 另外：根本沒有使用變量「n」。

Answer 2

你對遞歸的返回值什麼都不做。

這條線：

subset(list, n, target); 

應改爲：

if (subset(list, n, target)){ 
    return true; 
} 

而且，你沒有做任何事情與你n可變

---

我喜歡你正在努力男人，所以我會讓你更容易:)。

public static void main(String[] args) { 
    int[] array = {1, 2, 3, 4, 5}; 
    int n = 3; 
    int sum = 10; 
    System.out.println(subset(array, n, sum)); 
} 

public static boolean subset(int[] array, int n, int sum) { 
    //If I have enough numbers in my subarray, I can check, if it is equal to my sum 
    if (array.length == n) { 
     //If it is equal, I found subarray I was looking for 
     if (addArrayInt(array) == sum) { 
      return true; 
     } else { 
      return false; 
     } 
    } 

    //Trying all possibilites and doing recursion 
    for (int i = 0; i < array.length; i++) { 
     //if some recursion returned true, I found it, so I can also return true 
     int[] subarray = new int[array.length - 1]; 
     int k = 0; 
     for (int j = 0; j < subarray.length; j++) { 
      if (i == j) { 
       k++; 
      } 
      subarray[j] = array[j + k]; 
     } 
     if (subset(subarray, n, sum)) { 
      return true; 
     } 
    } 

    //If I didnt find anything, I have to return false 
    return false; 
} 

public static int addArrayInt(int[] array) { 
    int res = 0; 
    for (int i = 0; i < array.length; i++) { 
     res += array[i]; 
    } 
    return res; 
} 

但是，你不明白遞歸的基本知識，你很接近，但我認爲你錯過了主要想法:)。我建議你嘗試遞歸計算Factorial，然後嘗試Fibonacci，它可以提供幫助，並且在互聯網上有教程。