[leetcode]Missing Ranges

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public class Solution { public List<String> findMissingRanges(int[] nums, int lower, int upper) { List<String> result = new ArrayList<String>(); if (nums == null || nums.length == 0){ result.add(generateString(lower, upper)); return result; } int prev = lower-1; for (int i = 0; i < nums.length; i++){ if (nums[i]-prev >= 2){ result.add(generateString(prev+1, nums[i]-1)); } prev = nums[i]; } if (upper-nums[nums.length-1] > 0){ result.add(generateString(nums[nums.length-1]+1,upper)); } return result; } private String generateString(int from, int to){ return from == to?""+from:from+"->"+to; } }