163 Missing Ranges ****

Given a sorted integer arraynums, where the range of elements are in theinclusive range[lower,upper], return its missing ranges.

Example:

Input: nums = [0, 1, 3, 50, 75], lower = 0 and upper = 99,
Output: ["2", "4->49", "51->74", "76->99"]

崩溃

临界条件

必须用LONG 放LOW AND HIGH

class Solution {
    public List<String> findMissingRanges(int[] nums, int lower, int upper) {
        List<String> ans = new ArrayList<>();
        if (nums == null) {
            return ans;
        }
        //in case of 
        long low = lower;
        long high = upper;
        for (int num : nums) {
            if (num == low) {
                low++;
            } else if ( low < num ) {
                if (low + 1 == num) {
                    ans.add("" + low);
                } else {
                    ans.add(low + "->" + (num - 1));
                }
                low = (long)num + 1;
                ////////////////////this step is essential;
            }
        }
        if (low == high) {
            ans.add("" + low);
        } else if (low < high) {
            ans.add(low + "->" + high);
        }
        return ans;
    }
}