Height Checker Python Solution with Tests

LeetCode 1051, Easy. Topics: Array, Sorting, Counting Sort. View on LeetCode. Generate this problem as a practice environment: tested reference solution, 12 parametrized pytest cases, and a playground notebook:

lcpy gen -n 1051   # by problem number
lcpy gen -s height_checker   # by problem name

Problem

A school is trying to take an annual photo of all the students. The students are asked to stand in a single file line in non-decreasing order by height. Let this ordering be represented by the integer array expected where expected[i] is the expected height of the ith student in line. You are given an integer array heights representing the current order that the students are standing in. Each heights[i] is the height of the ith student in line (0-indexed). Return the number of indices where heights[i] != expected[i].

Examples

Input: heights = [1,1,4,2,1,3]
Output: 3
Explanation:
heights:  [1,1,4,2,1,3]
expected: [1,1,1,2,3,4]
Indices 2, 4, and 5 do not match.

Input: heights = [5,1,2,3,4]
Output: 5
Explanation:
heights:  [5,1,2,3,4]
expected: [1,2,3,4,5]
All indices do not match.

Input: heights = [1,2,3,4,5]
Output: 0
Explanation:
heights:  [1,2,3,4,5]
expected: [1,2,3,4,5]
All indices match.

Constraints

1 <= heights.length <= 100
1 <= heights[i] <= 100

Solution

Reference implementation from solution.py on GitHub, full suite in test_solution.py:

class Solution:
    # Time: O(n log n)
    # Space: O(n)
    def height_checker(self, heights: list[int]) -> int:
        expected = sorted(heights)
        return sum(a != b for a, b in zip(heights, expected, strict=True))

Complexity

Time	Space
O(n log n)	O(n)

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Height Checker Python Solution with Tests

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