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LeetCode 3109: Find the Index of Permutation Solution

Master LeetCode problem 3109 (Find the Index of Permutation), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

Problem Explanation

Explanation:

To find the index of a given permutation of a set of numbers, we can follow the below algorithm:

  1. Generate all permutations of the given set of numbers.
  2. Sort the permutations in lexicographical order.
  3. Find the position of the input permutation in the sorted list of permutations.

Time Complexity:

The time complexity of this approach is O(n!) where n is the number of elements in the input set.

Space Complexity:

The space complexity of this approach is O(n!) as well since we are storing all permutations.

Solution Code

import java.util.*;

class Solution {
    public int findIndexPermutation(int[] nums) {
        String target = Arrays.toString(nums).replaceAll("[,\\s\\[\\]]", "");
        List<String> permutations = new ArrayList<>();
        generatePermutations("", nums, new boolean[nums.length], permutations);
        Collections.sort(permutations);
        return permutations.indexOf(target);
    }

    private void generatePermutations(String current, int[] nums, boolean[] used, List<String> permutations) {
        if (current.length() == nums.length) {
            permutations.add(current);
            return;
        }
        for (int i = 0; i < nums.length; i++) {
            if (used[i]) continue;
            used[i] = true;
            generatePermutations(current + nums[i], nums, used, permutations);
            used[i] = false;
        }
    }
}

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What is the time complexity of LeetCode 3109 (Find the Index of Permutation)?

The time complexity for LeetCode 3109 (Find the Index of Permutation) varies by solution. Check the detailed explanation section for specific complexities in Java, C++, and Python implementations.

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