Off-by-one on range boundaries
Wrong move: Loop endpoints miss first/last candidate.
Usually fails on: Fails on minimal arrays and exact-boundary answers.
Fix: Re-derive loops from inclusive/exclusive ranges before coding.
Break down a hard problem into reliable checkpoints, edge-case handling, and complexity trade-offs.
You are given an array nums of n positive integers.
You can perform two types of operations on any element of the array any number of times:
2.
[1,2,3,4], then you can do this operation on the last element, and the array will be [1,2,3,2].2.
[1,2,3,4], then you can do this operation on the first element, and the array will be [2,2,3,4].The deviation of the array is the maximum difference between any two elements in the array.
Return the minimum deviation the array can have after performing some number of operations.
Example 1:
Input: nums = [1,2,3,4] Output: 1 Explanation: You can transform the array to [1,2,3,2], then to [2,2,3,2], then the deviation will be 3 - 2 = 1.
Example 2:
Input: nums = [4,1,5,20,3] Output: 3 Explanation: You can transform the array after two operations to [4,2,5,5,3], then the deviation will be 5 - 2 = 3.
Example 3:
Input: nums = [2,10,8] Output: 3
Constraints:
n == nums.length2 <= n <= 5 * 1041 <= nums[i] <= 109Problem summary: You are given an array nums of n positive integers. You can perform two types of operations on any element of the array any number of times: If the element is even, divide it by 2. For example, if the array is [1,2,3,4], then you can do this operation on the last element, and the array will be [1,2,3,2]. If the element is odd, multiply it by 2. For example, if the array is [1,2,3,4], then you can do this operation on the first element, and the array will be [2,2,3,4]. The deviation of the array is the maximum difference between any two elements in the array. Return the minimum deviation the array can have after performing some number of operations.
Start with the most direct exhaustive search. That gives a correctness anchor before optimizing.
Pattern signal: Array · Greedy · Segment Tree
[1,2,3,4]
[4,1,5,20,3]
[2,10,8]
Source-backed implementations are provided below for direct study and interview prep.
// Accepted solution for LeetCode #1675: Minimize Deviation in Array
class Solution {
public int minimumDeviation(int[] nums) {
PriorityQueue<Integer> q = new PriorityQueue<>((a, b) -> b - a);
int mi = Integer.MAX_VALUE;
for (int v : nums) {
if (v % 2 == 1) {
v <<= 1;
}
q.offer(v);
mi = Math.min(mi, v);
}
int ans = q.peek() - mi;
while (q.peek() % 2 == 0) {
int x = q.poll() / 2;
q.offer(x);
mi = Math.min(mi, x);
ans = Math.min(ans, q.peek() - mi);
}
return ans;
}
}
// Accepted solution for LeetCode #1675: Minimize Deviation in Array
func minimumDeviation(nums []int) int {
q := hp{}
mi := math.MaxInt32
for _, v := range nums {
if v%2 == 1 {
v <<= 1
}
heap.Push(&q, v)
mi = min(mi, v)
}
ans := q.IntSlice[0] - mi
for q.IntSlice[0]%2 == 0 {
x := heap.Pop(&q).(int) >> 1
heap.Push(&q, x)
mi = min(mi, x)
ans = min(ans, q.IntSlice[0]-mi)
}
return ans
}
type hp struct{ sort.IntSlice }
func (h *hp) Push(v any) { h.IntSlice = append(h.IntSlice, v.(int)) }
func (h *hp) Pop() any {
a := h.IntSlice
v := a[len(a)-1]
h.IntSlice = a[:len(a)-1]
return v
}
func (h *hp) Less(i, j int) bool { return h.IntSlice[i] > h.IntSlice[j] }
# Accepted solution for LeetCode #1675: Minimize Deviation in Array
class Solution:
def minimumDeviation(self, nums: List[int]) -> int:
h = []
mi = inf
for v in nums:
if v & 1:
v <<= 1
h.append(-v)
mi = min(mi, v)
heapify(h)
ans = -h[0] - mi
while h[0] % 2 == 0:
x = heappop(h) // 2
heappush(h, x)
mi = min(mi, -x)
ans = min(ans, -h[0] - mi)
return ans
// Accepted solution for LeetCode #1675: Minimize Deviation in Array
/**
* [1675] Minimize Deviation in Array
*
* You are given an array nums of n positive integers.
* You can perform two types of operations on any element of the array any number of times:
*
* If the element is even, divide it by 2.
*
* For example, if the array is [1,2,3,4], then you can do this operation on the last element, and the array will be [1,2,3,<u>2</u>].
*
*
* If the element is odd, multiply it by 2.
*
* For example, if the array is [1,2,3,4], then you can do this operation on the first element, and the array will be [<u>2</u>,2,3,4].
*
*
*
* The deviation of the array is the maximum difference between any two elements in the array.
* Return the minimum deviation the array can have after performing some number of operations.
*
* Example 1:
*
* Input: nums = [1,2,3,4]
* Output: 1
* Explanation: You can transform the array to [1,2,3,<u>2</u>], then to [<u>2</u>,2,3,2], then the deviation will be 3 - 2 = 1.
*
* Example 2:
*
* Input: nums = [4,1,5,20,3]
* Output: 3
* Explanation: You can transform the array after two operations to [4,<u>2</u>,5,<u>5</u>,3], then the deviation will be 5 - 2 = 3.
*
* Example 3:
*
* Input: nums = [2,10,8]
* Output: 3
*
*
* Constraints:
*
* n == nums.length
* 2 <= n <= 5 * 10^<span style="font-size: 10.8333px;">4</span>
* 1 <= nums[i] <= 10^9
*
*/
pub struct Solution {}
// problem: https://leetcode.com/problems/minimize-deviation-in-array/
// discuss: https://leetcode.com/problems/minimize-deviation-in-array/discuss/?currentPage=1&orderBy=most_votes&query=
// submission codes start here
impl Solution {
// Credit: https://leetcode.com/problems/minimize-deviation-in-array/solutions/3188337/just-a-runnable-solution/
pub fn minimum_deviation(nums: Vec<i32>) -> i32 {
let mut nums = nums;
let mut min = std::i32::MAX;
for num in nums.iter_mut() {
if *num % 2 == 1 {
*num *= 2;
}
min = min.min(*num);
}
let mut result = std::i32::MAX;
let mut heap = std::collections::BinaryHeap::new();
for num in nums {
heap.push(num);
}
while let Some(num) = heap.pop() {
result = result.min(num - min);
if num % 2 == 1 {
break;
}
min = min.min(num / 2);
heap.push(num / 2);
}
result
}
}
// submission codes end
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_1675_example_1() {
let nums = vec![1, 2, 3, 4];
let result = 1;
assert_eq!(Solution::minimum_deviation(nums), result);
}
#[test]
fn test_1675_example_2() {
let nums = vec![4, 1, 5, 20, 3];
let result = 3;
assert_eq!(Solution::minimum_deviation(nums), result);
}
#[test]
fn test_1675_example_3() {
let nums = vec![2, 10, 8];
let result = 3;
assert_eq!(Solution::minimum_deviation(nums), result);
}
}
// Accepted solution for LeetCode #1675: Minimize Deviation in Array
// Auto-generated TypeScript example from java.
function exampleSolution(): void {
}
// Reference (java):
// // Accepted solution for LeetCode #1675: Minimize Deviation in Array
// class Solution {
// public int minimumDeviation(int[] nums) {
// PriorityQueue<Integer> q = new PriorityQueue<>((a, b) -> b - a);
// int mi = Integer.MAX_VALUE;
// for (int v : nums) {
// if (v % 2 == 1) {
// v <<= 1;
// }
// q.offer(v);
// mi = Math.min(mi, v);
// }
// int ans = q.peek() - mi;
// while (q.peek() % 2 == 0) {
// int x = q.poll() / 2;
// q.offer(x);
// mi = Math.min(mi, x);
// ans = Math.min(ans, q.peek() - mi);
// }
// return ans;
// }
// }
Use this to step through a reusable interview workflow for this problem.
Try every possible combination of choices. With n items each having two states (include/exclude), the search space is 2ⁿ. Evaluating each combination takes O(n), giving O(n × 2ⁿ). The recursion stack or subset storage uses O(n) space.
Greedy algorithms typically sort the input (O(n log n)) then make a single pass (O(n)). The sort dominates. If the input is already sorted or the greedy choice can be computed without sorting, time drops to O(n). Proving greedy correctness (exchange argument) is harder than the implementation.
Review these before coding to avoid predictable interview regressions.
Wrong move: Loop endpoints miss first/last candidate.
Usually fails on: Fails on minimal arrays and exact-boundary answers.
Fix: Re-derive loops from inclusive/exclusive ranges before coding.
Wrong move: Locally optimal choices may fail globally.
Usually fails on: Counterexamples appear on crafted input orderings.
Fix: Verify with exchange argument or monotonic objective before committing.