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"].

Solution:

  1. public class Solution {
  2.   public List<String> summaryRanges(int[] a) {
  3.     List<String> res = new ArrayList<String>();
  5.     if (a == null) 
  6.       return res;
  8.     int i = 0, n = a.length;
  10.     for (int j = 1; j < n; j++) {
  11.       if ((long)a[j] - (long)a[j - 1] > 1) {
  12.         // found a range
  13.         res.add(getRange(a[i], a[j - 1]));
  14.         i = j;
  15.       }
  16.     }
  18.     // do a final check
  19.     if (i < n) 
  20.       res.add(getRange(a[i], a[n - 1]));
  22.     return res;
  23.   }
  25.   String getRange(int n1, int n2) {
  26.     return (n1 == n2) ? String.valueOf(n1) : String.format("%d->%d", n1, n2);
  27.   }
  28. }