LeetCode: Smallest Range II

Posted on September 28, 2018July 26, 2020 by braindenny

Smallest Range II

Similar Problems:

Given an array A of integers, for each integer A[i] we need to choose either x = -K or x = K, and add x to A[i] (only once).

After this process, we have some array B.

Return the smallest possible difference between the maximum value of B and the minimum value of B.

Example 1:

Input: A = [1], K = 0
Output: 0
Explanation: B = [1]

Example 2:

Input: A = [0,10], K = 2
Output: 6
Explanation: B = [2,8]

Example 3:

Input: A = [1,3,6], K = 3
Output: 3
Explanation: B = [4,6,3]

Note:

1 <= A.length <= 10000
0 <= A[i] <= 10000
0 <= K <= 10000

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

Solution:

// https://code.dennyzhang.com/smallest-range-ii
// Basic Ideas: greedy
//
//   Sort the list. The initial difference is A[N-1]-A[0]
//
//   Try to add for small values, subtract for big values
//   For the biggest value, we always substract. 
//   And for the smallest, we always add.
//
// Complexity: Time O(n*log(n)), Space O(1)
import "sort"
func min(x, y int)int {
    if x>y {
        return y
    } else {
        return x
    }
}

func max(x, y int)int {
    if x>y {
        return x
    } else {
        return y
    }
}

func smallestRangeII(A []int, K int) int {
    sort.Ints(A)
    res := A[len(A)-1]-A[0]
    for i:=0; i+1<len(A); i++ {
        high := max(A[len(A)-1]-K, A[i]+K)
        low := min(A[0]+K, A[i+1]-K)
        res = min(res, high-low)
    }
    return res
}

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