[LeetCode] Search Insert Position

Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.
You may assume no duplicates in the array.
Here are few examples.
[1,3,5,6], 5 → 2
[1,3,5,6], 2 → 1
[1,3,5,6], 7 → 4
[1,3,5,6], 0 → 0

Java Code:

public int searchInsert(int[] A, int target) {
      int start = 0;
      int end = A.length - 1;
      int index = start;
      
      while(start <= end){
          int middle = (start + end)/2;
          if(A[middle] == target) return middle;
          
          if(target < A[middle]){
              end = middle - 1;
              index = middle;
          }else{
              start = middle + 1;
              index = start;
          }
      }
      
      return index;
    }

[LeetCode] Search for a range

Given a sorted array of integers, find the starting and ending position of a given target value.
Your algorithm's runtime complexity must be in the order of O(log n).
If the target is not found in the array, return [-1, -1].
For example,
Given [5, 7, 7, 8, 8, 10] and target value 8,
return [3, 4].


解题思路：
利用二分搜索法分别找到beginindex 和 endindex.

Java Code:

  public int[] searchRange(int[] A, int target) {
        int[] result = new int[2];
        
        result[0] = searchRange1(A, target, true);
        result[1] = searchRange1(A, target, false);
        
        return result;
    }
    
    //binary search for beginIndex and endIndex respectily 
     public int searchRange1(int[] A, int target, boolean first){
           int start = 0, end = A.length - 1;
           int index = -1;
           
           while(start <= end){
               int middle = (start + end)/2;
               
               if(A[middle] > target){
                   end = middle - 1;
               }
               
               if(A[middle] < target){
                   start = middle + 1;
               }
               
               if(A[middle] == target){
                   index = middle;
                   
                   if(first) end = middle-1;
                   else start = middle + 1;
               }
           }
          
           return index;
    }