Today I have done leetcode's June LeetCoding Challenge with cpp.

June LeetCoding Challenge 12

Description

Summary Ranges

You are given a sorted unique integer array nums.

A range [a,b] is the set of all integers from a to b (inclusive).

Return the smallest sorted list of ranges that cover all the numbers in the array exactly. That is, each element of nums is covered by exactly one of the ranges, and there is no integer x such that x is in one of the ranges but not in nums.

Each range [a,b] in the list should be output as:

• "a->b" if a != b
• "a" if a == b

Example 1:

Input: nums = [0,1,2,4,5,7]
Output: ["0->2","4->5","7"]
Explanation: The ranges are:
[0,2] --> "0->2"
[4,5] --> "4->5"
[7,7] --> "7"

Example 2:

Input: nums = [0,2,3,4,6,8,9]
Output: ["0","2->4","6","8->9"]
Explanation: The ranges are:
[0,0] --> "0"
[2,4] --> "2->4"
[6,6] --> "6"
[8,9] --> "8->9"

Constraints:

• 0 <= nums.length <= 20
• -231 <= nums[i] <= 231 - 1
• All the values of nums are unique.
• nums is sorted in ascending order.

Solution

class Solution {
  string toRange(int begin, int end) {
    if(begin == end) return to_string(begin);
    return to_string(begin) + "->" + to_string(end);
  }
public:
  vector<string> summaryRanges(vector<int>& nums) {
    if(nums.empty()) return {};
    vector<string> answer;
    int begin = nums.front();
    int end = nums.front();
    for(auto n : nums) {
      if(n > min(end, INT_MAX - 1) + 1) {
        answer.push_back(toRange(begin, end));
        begin = end = n;
      } else {
        end = n;
      }
    }
    answer.push_back(toRange(begin, end));
    return answer;
  }
};

// Accepted
// 30/30 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 57.22 % of cpp submissions (6.8 MB)