Compress a Sorted List Into Ranges
Problem
Given a sorted array of distinct integers, return the smallest list of ranges covering every value. A range like "2-5" stands for any maximal run of consecutive numbers; a singleton like "7" stands for one value with no neighbour. Walk the array remembering the start of the current run; emit a range each time the run breaks.
Input
nums = [0,1,2,4,5,7]Output
["0->2","4->5","7"]Three runs: 0..2, 4..5, and a lone 7.
def summary_ranges(nums):
out = []
i = 0
while i < len(nums):
j = i
while j + 1 < len(nums) and nums[j + 1] == nums[j] + 1:
j += 1
out.append(str(nums[i]) if i == j else f"{nums[i]}->{nums[j]}")
i = j + 1
return outfunction summaryRanges(nums) {
const out = [];
let i = 0;
while (i < nums.length) {
let j = i;
while (j + 1 < nums.length && nums[j + 1] === nums[j] + 1) j++;
out.push(i === j ? String(nums[i]) : nums[i] + "->" + nums[j]);
i = j + 1;
}
return out;
}class Solution {
public List<String> summaryRanges(int[] nums) {
List<String> out = new ArrayList<>();
int i = 0;
while (i < nums.length) {
int j = i;
while (j + 1 < nums.length && nums[j + 1] == nums[j] + 1) j++;
out.add(i == j ? String.valueOf(nums[i]) : nums[i] + "->" + nums[j]);
i = j + 1;
}
return out;
}
}vector<string> summaryRanges(vector<int>& nums) {
vector<string> out;
int i = 0;
while (i < (int)nums.size()) {
int j = i;
while (j + 1 < (int)nums.size() && nums[j + 1] == nums[j] + 1) ++j;
if (i == j) out.push_back(to_string(nums[i]));
else out.push_back(to_string(nums[i]) + "->" + to_string(nums[j]));
i = j + 1;
}
return out;
}