LeetCode-in-Rust

46. Permutations

Medium

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

Example 1:

Input: nums = [1,2,3]

Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

Example 2:

Input: nums = [0,1]

Output: [[0,1],[1,0]]

Example 3:

Input: nums = [1]

Output: [[1]]

Constraints:

• 1 <= nums.length <= 6
• -10 <= nums[i] <= 10
• All the integers of nums are unique.

Solution

impl Solution {
    pub fn permute(nums: Vec<i32>) -> Vec<Vec<i32>> {
        if nums.is_empty() {
            return vec![];
        }

        let mut final_result = Vec::new();
        let mut curr_result = Vec::new();
        let mut used = vec![false; nums.len()];

        Solution::permute_recur(&nums, &mut final_result, &mut curr_result, &mut used);
        final_result
    }

    fn permute_recur(
        nums: &[i32],
        final_result: &mut Vec<Vec<i32>>,
        curr_result: &mut Vec<i32>,
        used: &mut Vec<bool>,
    ) {
        if curr_result.len() == nums.len() {
            final_result.push(curr_result.clone());
            return;
        }

        for i in 0..nums.len() {
            if used[i] {
                continue;
            }

            curr_result.push(nums[i]);
            used[i] = true;

            Solution::permute_recur(nums, final_result, curr_result, used);

            used[i] = false;
            curr_result.pop();
        }
    }
}

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