Leetcode 3431. Minimum Unlocked Indices to Sort Nums

Given an array and a set of locked indices that cannot change, find the minimum number of indices you must unlock so that by permuting values on the unlocked positions the whole array can be sorted non-decreasingly. The core challenge is to determine which mismatches with the sorted array can be fixed using existing unlocked values (often via greedy/multiset matching) to minimize newly unlocked positions.