Java - 傳遞一個數組，但它正在丟棄元素

Question

private static void split(int arr[], int low, int high){ 
    int[] newArr = arr; 
    //Split num of coins into 3 sub arrays 
    int mid1 = (int) Math.floor((low+high)/3); 
    int mid2 = (int) Math.floor((low+high)/1.5); 

    for(int i=0; i<= high; i++){ 
     System.out.print("newArr:"+newArr[i]+", "); 

    } 
    System.out.print("mid1:"+mid1+" mid2:"+mid2+"\n"); 

    int[] a = new int[mid1+1]; 
    int[] b = new int[mid1+1]; 
    int[] c = new int[mid1+1]; 
    int i, j, k; 

    for(i=0; i<= mid1; i++){ //1,2,3 
     a[i] = arr[i]; 
     System.out.println("a"+a[i]); 
    } 
    i=0; 
    for(j=mid1+1; j<=mid2; j++){ //4,5,6 
     b[i] = arr[j]; 
     System.out.println("b"+b[i]); 
     i++; 
    } 
    i=0; 
    for(k=mid2+1; k<=high; k++){ //7,8,9 
     c[i] = arr[k]; 
     System.out.println("c"+c[i]); 
     i++; 
    } 
    System.out.print("a: "); 
    for(i=0;i<a.length;i++){ 
     System.out.print(a[i]+", "); 
    } 
    System.out.print("b: "); 
    for(i=0;i<b.length;i++){ 
     System.out.print(b[i]+", "); 
    } 
    System.out.print("c: "); 
    for(i=0;i<c.length;i++){ 
     System.out.print(c[i]+", "); 
    } 
    System.out.println(""); 

    //Compare 
    int sumA=0, sumB=0; 
    for(i=0; i<a.length; i++){ 
     sumA += a[i]; 
    } 
    System.out.println("sumA:"+sumA); 
    for(j=0; j<b.length; j++){ 
     sumB += b[j]; 
    } 
    System.out.println("sumB:"+sumB); 

    if(sumA > sumB){ 
     //check if element is last coin in arr 
     if(a.length == 1){ 
      System.out.print("You've found the coin in a!"); 
     } else { 
      //split a 
      System.out.println("split a: "); 
      split(a, a[0], a[a.length - 1]); 
     } 
    } 
    else if(sumB > sumA){ 
     //check if element is last coin in arr 
     if(b.length == 1){ 
      System.out.print("You've found the coin in b!"); 
     } else { 
      //split b 
      System.out.println("split b: "); 
      System.out.print("b: "); 
      for(i=0;i<b.length;i++){ 
       System.out.print(b[i]+", "); 
      } 
      split(b, b[0], b[b.length-1]); 
     } 
    } 
    else{ 
     //check if element is last coin in arr 
     if(c.length == 1){ 
      System.out.print("You've found the coin in c!"); 
     } else { 
      //split orig last 3 
      System.out.println("split c: "); 
      split(c, c[0], c[c.length - 1]); 
     } 
    } 

} 

我的原始數組= = int [] arr = {0,0,0,0,1,0,0,0,0}; 我試圖找到價值之一。一旦它通過split函數，值0,1,0將在數組b中，因此它將再次調用split，但是當您在split中檢查newArr時，它只有0值，而不是0,1 ，0。爲什麼我的元素消失。

P.S有很多打印語句，我一直在試圖弄清楚爲什麼它沒有抓住第一次運行和第二次運行之間的所有元素，抱歉。

Answer 1

你有一個問題是，mid1和mid2被打破，如果低> 0

int mid1 = (int) Math.floor((low+high)/3); 
int mid2 = (int) Math.floor((low+high)/1.5); 

如果你想MID1和MID2是1/3，差的2/3，你需要把它寫的是方式

int dif = high - low; 
int mid1 = low + dif/3; 
int mid2 = high - dif /3; 
//or 
int mid2 = low + 2 * dif/3; 

或者你可以用寫成一個襯墊

int mid1 = (2 * low + high)/3; 
int mid2 = (low + 2 * high)/3; 

另外這個代碼

int[] a = new int[mid1+1]; 
int[] b = new int[mid1+1]; 
int[] c = new int[mid1+1]; 

還假定low == 0否則，你想要的是

int[] a = new int[mid1 - low]; // how many in the first part 
int[] b = new int[mid2 - mid1]; // how many in the second part 
int[] c = new int[high - mid2]; // how many in the third part 

最後這行是沒有意義的

split(a, a[0], a[a.length - 1]); 

如果a包含[100, 200, 300]你不會拆對100至300。你大概的意思是

split(a, 0, a.length); 

，你會注意到實際上是

split(arr, low, mid1); 

這意味着你不需要在任何時候採取數組的一個副本。