LeetCode: Summary Ranges

// https://code.dennyzhang.com/summary-ranges
// Basic Ideas: twopointer + simulation
//
// Complexity: Time O(n), Space O(1)
func summaryRanges(nums []int) []string {
    res := []string{}
    // nums[i...j]
    i := 0
    for j:=0; j<len(nums); j++ {
        if j+1<len(nums) && nums[j]+1 == nums[j+1] {
            continue
        }
       // last group or group ends
        if i==j {
            res = append(res, fmt.Sprintf("%d", nums[i]))
        } else {
            res = append(res, fmt.Sprintf("%d->%d", nums[i], nums[j]))
        }
        // need to start a new group
        i = j+1
    }
    return res
}

// https://code.dennyzhang.com/summary-ranges
// Basic Ideas: twopointer + simulation
//
// Complexity: Time O(n), Space O(1)
func summaryRanges(nums []int) []string {
    res := []string{}
    // nums[i...j]
    i := 0
    for j:=0; j<len(nums); j++ {
        if j == len(nums)-1 || nums[j]+1 != nums[j+1] {
           // last group or group ends
            if i==j {
                res = append(res, fmt.Sprintf("%d", nums[i]))
            } else {
                res = append(res, fmt.Sprintf("%d->%d", nums[i], nums[j]))
            }

            if nums[j]+1 != nums[j] {
                // need to start a new group
                i = j+1
            }
        }
    }
    return res
}

## https://code.dennyzhang.com/summary-ranges
## Basic Ideas: 2 pointer
## Complexity: Time O(n), Space O(1)
## Assumptions:
class Solution(object):
    def summaryRanges(self, nums):
        """
        :type nums: List[int]
        :rtype: List[str]
        """
        res = []
        length = len(nums)
        i=0
        while i<length:
            j = i + 1
            while j<length and nums[j] == nums[j-1] + 1:
                j += 1
            if j != i+1:
                res.append("%d->%d" % (nums[i], nums[j-1]))
            else:
                res.append("%d" % nums[i])
            i = j
        return res