LeetCode 2340: Minimum Adjacent Swaps to Make a Valid Array Solution

Master LeetCode problem 2340 (Minimum Adjacent Swaps to Make a Valid Array), 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.

2340. Minimum Adjacent Swaps to Make a Valid Array

Medium

Array Greedy

Problem Explanation

Explanation:

This problem asks us to find the minimum number of adjacent swaps needed to make an array valid. An array is considered valid if all elements are distinct and each element is at the correct position. We can solve this problem by constructing a graph where each element is connected to its correct position. Then, we perform a cycle counting algorithm to find the cycles in the graph. The minimum number of swaps needed is equal to the sum of the sizes of the cycles minus 1.

Algorithm:

Create a mapping of element to index for easy access to the correct positions.
Initialize a visited array to track visited elements.
For each element in the array, if it is already visited, continue to the next element.
Otherwise, start a cycle count from the current element by traversing through the graph until we reach the starting element.
The size of the cycle gives us the number of swaps needed for that cycle.
Repeat steps 3-5 until all elements are visited.
The total number of swaps needed is the sum of sizes of all cycles minus the number of cycles.

Time Complexity:

The time complexity of this algorithm is O(n), where n is the number of elements in the array.

Space Complexity:

The space complexity of this algorithm is O(n) for storing the mapping and visited array.

: :

Solution Code

class Solution {
    public int minSwaps(int[] data) {
        int n = data.length;
        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < n; i++) {
            map.put(data[i], i);
        }
        
        boolean[] visited = new boolean[n];
        int swaps = 0;
        
        for (int i = 0; i < n; i++) {
            if (visited[i] || data[i] == i) {
                continue;
            }
            
            int cycleSize = 0;
            int j = i;
            while (!visited[j]) {
                visited[j] = true;
                j = map.get(j);
                cycleSize++;
            }
            swaps += cycleSize - 1;
        }
        
        return swaps;
    }
}

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