How hard is LeetCode 1182. Shortest Distance to Target Color?

LeetCode 1182. Shortest Distance to Target Color is rated Medium on LeetCode.

What is the time complexity of LeetCode 1182. Shortest Distance to Target Color?

The Python solution on this page runs in O(n).

What is the space complexity of LeetCode 1182. Shortest Distance to Target Color?

The Python solution on this page uses O(n) auxiliary space.

What topics does LeetCode 1182. Shortest Distance to Target Color cover?

LeetCode 1182. Shortest Distance to Target Color is tagged Array, Binary Search and Dynamic Programming on LeetCode.

Is LeetCode 1182. Shortest Distance to Target Color a premium problem?

Yes. LeetCode 1182. Shortest Distance to Target Color is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.

Shortest Distance to Target Color — LeetCode 1182 Python Solution

MediumLeetCode PremiumArrayBinary SearchDynamic Programming

Problem: #1182
Pattern: Monotonic Stack
Reading time: 4 min
Source: leetcode.com

The problem

You are given an array colors, in which there are three colors: 1, 2 and 3. You are also given some queries.

Example

Input: colors = [1,1,2,1,3,2,2,3,3], queries = [[1,3],[2,2],[6,1]]
Output: [3,0,3]
Explanation: The nearest 3 from index 1 is at index 4 (3 steps away).

Python solution

Python

class Solution:
    def shortestDistanceColor(
        self, colors: List[int], queries: List[List[int]]
    ) -> List[int]:
        n = len(colors)
        right = [[inf] * 3 for _ in range(n + 1)]
        for i in range(n - 1, -1, -1):
            for j in range(3):
                right[i][j] = right[i + 1][j]
            right[i][colors[i] - 1] = i
        left = [[-inf] * 3 for _ in range(n + 1)]
        for i, c in enumerate(colors, 1):
            for j in range(3):
                left[i][j] = left[i - 1][j]
            left[i][c - 1] = i - 1
        ans = []
        for i, c in queries:
            d = min(i - left[i + 1][c - 1], right[i][c - 1] - i)
            ans.append(-1 if d > n else d)
        return ans

Complexity

Measure	Complexity
Time	O(n)
Space	O(n) auxiliary

Pattern: Monotonic Stack

Answer "what is the next greater element" for every position in one pass. LeetCode 1182. Shortest Distance to Target Color is filed here because the reference solution below belongs to the algorithm family this hub collects, even though its LeetCode tags point elsewhere.

The monotonic stack guide has the Python template for the pattern and the 225 LeetCode problems that use it.

Frequently asked questions

How hard is LeetCode 1182. Shortest Distance to Target Color?: LeetCode 1182. Shortest Distance to Target Color is rated Medium on LeetCode.
What is the time complexity of LeetCode 1182. Shortest Distance to Target Color?: The Python solution on this page runs in O(n).
What is the space complexity of LeetCode 1182. Shortest Distance to Target Color?: The Python solution on this page uses O(n) auxiliary space.
What topics does LeetCode 1182. Shortest Distance to Target Color cover?: LeetCode 1182. Shortest Distance to Target Color is tagged Array, Binary Search and Dynamic Programming on LeetCode.
Is LeetCode 1182. Shortest Distance to Target Color a premium problem?: Yes. LeetCode 1182. Shortest Distance to Target Color is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.