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leetcode_summary ranges

admin 11月 13, 2020 0

Summary Ranges

Given a sorted integer array without duplicates, return the summary of its ranges.
（将数组中连续的范围合并）

Example:

1. 设置标志位 left

具体实现过程如下：

class :
    def summaryRanges(self, nums: List[int]) -> List[str]:
        n = len(nums)
        if not n:
            return []
        
        results = []
        left = -1
        for i in range(n-1):
            if nums[i] == nums[i+1] - 1:
                if left == -1:
                    left = i
            else:
                if left == -1:
                    results.append(str(nums[i]))
                else:
                    results.append("%s->%s"%(str(nums[left]), str(nums[i])))
                    left = -1
        if left == -1:
            results.append(str(nums[n-1]))
        else:
            results.append("%s->%s"%(str(nums[left]), str(nums[n-1])))
                    
        return results

2. 直接统计range

在遍历数组的过程中不断地更新统计中range的右界，具体实现过程如下：

def summaryRanges(self, nums):
    ranges = []
    for n in nums:
        if not ranges or n > ranges[-1][-1] + 1:
            ranges += [],
        ranges[-1][1:] = n,
    return ['->'.join(map(str, r)) for r in ranges]