Missing Ranges

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

For example, given [0, 1, 3, 50, 75], lower = 0 and upper = 99, return ["2", "4->49", "51->74", "76->99"].

Tips:

增加pre和after来判断！

Code：

public class Solution {
    public List<String> findMissingRanges(int[] A, int lower, int upper) {
        List<String> result = new ArrayList<String>();
        int pre = lower - 1;
        for(int i = 0 ; i <= A.length  ; i++){
            int after = i == A.length ? upper + 1 : A[i]; 
            if(pre + 2 == after){
                result.add(String.valueOf(pre + 1));
            }else if(pre + 2 < after){
                result.add(String.valueOf(pre + 1) + "->" + String.valueOf(after - 1));
            }
            pre = after;
        }
        return result;
    }
}