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"].

一刷

public class Solution {
    public List<String> summaryRanges(int[] nums) {
        List<String> res = new ArrayList<>();
        if(nums == null || nums.length==0) return res;
        
        int left = nums[0], next = left+1;
        for(int i=1; i<nums.length; i++){
            if(nums[i] == next) next++;
            else{
                res.add(getRange(left, next-1));
                left = nums[i];
                next = left+1;
            }
        }
        res.add(getRange(left, next-1));
        return res;
        
    }
    
    private String getRange(int a, int b){
        if(a == b) return String.valueOf(a);
        StringBuilder sb = new StringBuilder();
        sb.append(a);
        sb.append("->");
        sb.append(b);
        return sb.toString();
    }
}