FirstAndLastPosition.java

public class FirstAndLastPosition {
    public static void main(String[] args) {

    }

    public int[] searchRange(int[] nums, int target) {

        int[] ans = { -1, -1 };
        // check for first occurrence if target first
        ans[0] = search(nums, target, true);
        if (ans[0] != -1) {
            ans[1] = search(nums, target, false);
        }
        return ans;
    }

    // this function just returns the index value of target
    int search(int[] nums, int target, boolean findStartIndex) {
        int ans = -1;
        int start = 0;
        int end = nums.length - 1;
        while (start <= end) {
            // find the middle element
            // int mid = (start + end) / 2; // might be possible that (start + end) exceeds
            // the range of int in java
            int mid = start + (end - start) / 2;

            if (target < nums[mid]) {
                end = mid - 1;
            } else if (target > nums[mid]) {
                start = mid + 1;
            } else {
                // potential ans found
                ans = mid;
                if (findStartIndex) {
                    end = mid - 1;
                } else {
                    start = mid + 1;
                }
            }
        }
        return ans;
    }
}