Java BinarySearch

Question

Can I get some help please? I have tried many methods to get this to work i got the array sorted and to print but after that my binary search function doesnt want to run and

Answer 1

Here is a solution without heap. The same thing can be done in an array. If we need to find 'k' largest numbers, we take an array of size 'k' populated with first k items from the main data source. Now, keep on reading an item, and place it in the result array, if it has a place.

public static void largestkNumbers() {
    int k = 4;    // find 4 largest numbers
    int[] arr = {4,90,7,10,-5,34,98,1,2};
    int[] result = new int[k];

    //initial formation of elems
    for (int i = 0; i < k; ++i) {
      result[i] = arr[i];
    }
    Arrays.sort(result);

    for ( int i = k; i < arr.length; ++i ) {
      int index = binarySearch(result, arr[i]);
      if (index > 0) {
        // insert arr[i] at result[index] and remove result[0]
        insertInBetweenArray(result, index, arr[i]);
      }
    }
  }

  public static void insertInBetweenArray(int[] arr, int index, int num) {
    // insert num at arr[index] and remove arr[0]
    for ( int i = 0 ; i < index; ++i ) {
      arr[i] = arr[i+1];
    }
    arr[index-1] = num;
  }

  public static int binarySearch(int[] arr, int num) {

    int lo = 0;
    int hi = arr.length - 1;
    int mid = -1;

    while( lo <= hi ) {
      mid = (lo+hi)/2;
      if ( arr[mid] > num ) {
        hi = mid-1;
      } else if ( arr[mid] < num ) {
        lo = mid+1;
      } else {
        return mid;
      }
    }
    return mid;
  }