LeetCode: Summary Ranges

LeetCode: Summary Ranges

Given a sorted integer array without duplicates, return the summary of its ranges.
For example, given [0,1,2,4,5,7], return ["0->2","4->5","7"].

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
public class SummaryRanges {
public List<String> summaryRanges(int[] nums) {
List<String> result = new ArrayList<String>();
if(nums == null || nums.length == 0) {
return result;
}

int head, last;
head = last = nums[0];
for(int i = 1; i < nums.length;i++) {
int x = nums[i];
if(last+1 != x) {
result.add(helper(head, last));
head = last = x;
} else {
last = x;
}
}
// do not forget the last pair
result.add(helper(head, last));
return result;
}

private String helper(int a, int b) {
if(a == b) {
return a +"";
} else {
return a+"->"+b;
}
}
}