[LeetCode] 228. Summary Ranges

Given a sorted integer array without duplicates, return the summary of its ranges.

Example 1:

Input:  [0,1,2,4,5,7]
Output: ["0->2","4->5","7"]
Explanation: 0,1,2 form a continuous range; 4,5 form a continuous range.

Example 2:

Input:  [0,2,3,4,6,8,9]
Output: ["0","2->4","6","8->9"]
Explanation: 2,3,4 form a continuous range; 8,9 form a continuous range.

题目：输入一个有序且无重复的整数数组，返回此数组中整数的连续取值范围。

实现思路：双指针找连续取值的起点和终点即可。题目输入的数组已经是排序且无重复的，所以end从start开始，只需要判断与nums[end+1] - nums[end]是否等于1即可，另外需要注意的是找到end后，start要移动到end+1的位置。

class Solution {
    public List summaryRanges(int[] nums) {
       List answer = new ArrayList<>();
        
        int i = 0;
        while (i < nums.length) {
        	StringBuilder sb = new StringBuilder();
        	sb.append(nums[i]);
        	
        	int j = i;
        	while (++j < nums.length)
        		if (nums[j] - nums[j - 1] != 1)
        			break;
        	
        	if (j > i + 1)
        		sb.append("->" + nums[j - 1]);
        	answer.add(sb.toString());
        	
        	i = j;
        }
        
        return answer;
    }
}