Binary-Search-2/Problem1.java at master · YogeshPardeshi/Binary-Search-2 · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
class Problem1 {
    public int[] searchRange(int[] nums, int target) {


        int first = binarySearchFirst(nums, target, 0, nums.length-1);

        if(first == -1) return new int[]{-1,-1};

        int last = binarySearchLast(nums, target, first, nums.length-1);

        return new int[]{first, last};
    }

    private int binarySearchFirst(int[] nums, int target, int low, int high){

        while(low <= high){
            int mid = low + (high - low)/2;
            if(nums[mid] == target){
                if(mid == 0 || nums[mid-1] != target){
                    return mid;
                }else{
                    high = mid - 1;
                }
            }else if(nums[mid] > target){
                high = mid - 1;
            }else{
                low = mid + 1;
            }
        }

        return -1;
    }

    private int binarySearchLast(int[] nums, int target, int low, int high){

        while(low <= high){
            int mid = low + (high - low)/2;
            if(nums[mid] == target){
                if(mid == nums.length-1 || nums[mid+1] != target){
                    return mid;
                }else{
                    low = mid + 1;
                }
            }else if(nums[mid] > target){
                high = mid - 1;
            }else{
                low = mid + 1;
            }
        }

        return -1;
    }
}