Leetcode-Missing Ranges

 1 public class Solution {
 2     public List<String> findMissingRanges(int[] A, int lower, int upper) {
 3         //for a range lower-upper, and a number A[i], we have conditions:
 4         //1. A[i]<lower: move to i+1;
 5         //2. A[i]==lower: lower -> A[i]+1
 6         //3. lower<A[i]<=upper: generate a range: lower->A[i]-1; lower becomes A[i]+1. NOTE A[i]==upper: end of the program.
 7         //4. A[i]>upper: get range: lower->upper, end of the problem.
 8 
 9         List<String> res = new ArrayList<String>();
10 
11         for (int i=0;i<A.length;i++){
12             if (A[i]<lower) continue;
13            
14             if (A[i]==lower){
15                 lower=A[i]+1;
16                 continue;
17             }
18 
19             if (A[i]>lower && A[i]<=upper){
20                 String range = "";
21                 if (lower!=A[i]-1) range = Integer.toString(lower)+"->"+Integer.toString(A[i]-1);
22                 else range = Integer.toString(lower);
23                 res.add(range);
24                 lower = A[i]+1;
25                 if (A[i]==upper) break;
26                 else continue;
27             }
28 
29             if (A[i]>upper){
30                 String range = "";
31                 if (lower!=upper) range = Integer.toString(lower)+"->"+Integer.toString(upper);
32                 else range = Integer.toString(lower);
33                 res.add(range);
34                 lower = A[i]+1;
35                 break;
36             }
37         }
38 
39         if (lower<=upper){
40             String range = "";
41             if (lower!=upper) range = Integer.toString(lower)+"->"+Integer.toString(upper);
42             else range = Integer.toString(lower);
43             res.add(range);
44         }
45 
46         return res;
47     }
48 }