生成有效数组的最少交换次数

/*
 * Problem: Minimum Swaps to Make Array Increasing
 * Given an array nums, you are allowed to swap any two elements in the array.
 * Return the minimum number of swaps needed to make the array strictly increasing.
 * 
 * Approach:
 * 1. Convert the array to a stream and sort it.
 * 2. Map each element to its index in the sorted array.
 * 3. Calculate the minimum swaps by finding cycles in the mapped indices.
 */

import java.util.*;
import java.util.stream.*;

public class MinimumSwapsStream {
    public int minSwaps(int[] nums) {
        int n = nums.length;
        int[] sortedNums = Arrays.stream(nums).sorted().toArray();
        Map<Integer, Integer> numToIndex = IntStream.range(0, n).boxed().collect(Collectors.toMap(i -> sortedNums[i], i -> i));
        boolean[] visited = new boolean[n];
        int swaps = 0;

        for (int i = 0; i < n; i++) {
            if (visited[i] || nums[i] == sortedNums[i]) continue;

            int cycleSize = 0;
            int x = i;
            while (!visited[x]) {
                visited[x] = true;
                x = numToIndex.get(nums[x]);
                cycleSize++;
            }

            if (cycleSize > 0) {
                swaps += (cycleSize - 1);
            }
        }

        return swaps;
    }

    public static void main(String[] args) {
        MinimumSwapsStream solution = new MinimumSwapsStream();
        int[] nums = {4, 3, 2, 1};
        System.out.println(solution.minSwaps(nums)); // Output should be 2
    }
}