Java - 传递一个数组，但它正在丢弃元素

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]); 
     } 
    } 

} 

我的原始数组= = int [] arr = {0,0,0,0,1,0,0,0,0}; 我试图找到价值之一。一旦它通过split函数，值0,1,0将在数组b中，因此它将再次调用split，但是当您在split中检查newArr时，它只有0值，而不是0,1 ，0。为什么我的元素消失。

P.S有很多打印语句，我一直在试图弄清楚为什么它没有抓住第一次运行和第二次运行之间的所有元素，抱歉。

Answer 1

你有一个问题是，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，你需要把它写的是方式

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

或者你可以用写成一个衬垫

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

另外这个代码

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

还假定low == 0否则，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 

最后这行是没有意义的

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

如果a包含[100, 200, 300]你不会拆对100至300。你大概的意思是

split(a, 0, a.length); 

，你会注意到实际上是

split(arr, low, mid1); 

这意味着你不需要在任何时候采取数组的一个副本。