summaryRanges.js

////////////////////////////////////////////////Summary Ranges/////////////////////////////////////////////
// You are given a sorted unique integer array nums.
// 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"
// Example 3:
// Input: nums = []
// Output: []
// Example 4:
// Input: nums = [-1]
// Output: ["-1"]
// Example 5:
// Input: nums = [0]
// Output: ["0"]
/**
 * @param {number[]} nums
 * @return {string[]}
 */
 const summaryRanges = function(nums) {
    let res = [], left = nums[0];
    for (let i = 0; i < nums.length; i++) {
        if (nums[i] + 1 !== nums[i + 1]) {
            res.push(left === nums[i] ? '' + nums[i] : left + '->' + nums[i]);
            left = nums[i + 1];
        }
    }
    return res;
};

// console.log(summaryRanges([0,1,2,4,5,7]));
// console.log(summaryRanges([0,2,3,4,6,8,9]));
// console.log(summaryRanges([]));
// console.log(summaryRanges([-1]));
// console.log(summaryRanges([0]));