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.
Thoughts
双指针指向当前范围，相连就让右边的指针一直往前直到i == len(nums) - 1 or num != nums[i + 1] - 1。
Code
class Solution:
def summaryRanges(self, nums: List[int]) -> List[str]:
res, beg = [], None
for i, num in enumerate(nums):
if beg is None: beg = num
if i == len(nums) - 1 or num != nums[i + 1] - 1:
if num == beg:
res.append(str(num))
else:
res.append(str(beg) + '->' + str(num))
beg = None
return res
class Solution {
public List<String> summaryRanges(int[] nums) {
List<String> res = new ArrayList<>();
for (int i = 0, pos = 0; i < nums.length; i++) {
if (i == nums.length - 1 || nums[i + 1] != nums[i] + 1) {
if (pos != i) {
res.add(nums[pos] + "->" + nums[i]);
} else {
res.add(nums[pos] + "");
}
pos = i;
pos++;
}
}
return res;
}
}