[알고리즘] Missing Ranage

Problem

int[] nums = {2, 3, 5, 10, 75};
int lower = 0, upper = 99;

Output : [0->1,4,6->49,51-74,76->99]

 

Code

import java.util.ArrayList;
import java.util.List;

public class MissingRange {
    public List<String> solution(int low, int upper, int[] nums) {
        List<String> result = new ArrayList<>();
        if(nums == null || nums.length == 0) return result;

        if (low < nums[0]) {
            result.add(makeRange(low, nums[0]-1));
        }
        for (int i = 0; i < nums.length-1; i++) {
            if (nums[i] != nums[i + 1] && nums[i] + 1 < nums[i+1]) {
                result.add(makeRange(nums[i]+1, nums[i+1]-1));
            }
        }
        if (nums[nums.length - 1] < upper) {
            result.add(makeRange(nums[nums.length - 1]+1, upper));

        }
        return result;
    }

    public List<String> solution2(int low, int upper, int[] nums) {
        List<String> result = new ArrayList<>();
        for (int i = 0; i < nums.length; i++) {
            int start, end;
            if (i == 0)
                start = low;
            else
                start = nums[i-1]+1;

            if(start == nums[i]) continue;
            end = nums[i] - 1;

            result.add(makeRange(start, end));
        }
        if (nums[nums.length - 1] < upper) {
            result.add(makeRange(nums[nums.length - 1] + 1, upper));
        }
        return result;
    }
    private String makeRange(int low, int high) {
        return low == high ? String.valueOf(low) : (low + "->" + high);
    }
    public static void main(String[] args) {
        int[] nums = new int[]{2,3,5,50,75};
        MissingRange problem = new MissingRange();
        System.out.println(problem.solution(0, 99, nums));
        System.out.println(problem.solution2(0, 99, nums));
    }
}