Generator.java

package git.snippet.common;

import java.util.Arrays;

public class Generator {
    // for test
    // 几乎有序的数组排序测试
    public static int[] randomArrayNoMoveMoreK(int maxSize, int maxValue, int K) {
        int[] arr = new int[(int) ((maxSize + 1) * Math.random())];
        for (int i = 0; i < arr.length; i++) {
            arr[i] = (int) ((maxValue + 1) * Math.random()) - (int) (maxValue * Math.random());
        }
        // 先排个序
        Arrays.sort(arr);
        // 然后开始随意交换，但是保证每个数距离不超过K
        // swap[i] == true, 表示i位置已经参与过交换
        // swap[i] == false, 表示i位置没有参与过交换
        boolean[] isSwap = new boolean[arr.length];
        for (int i = 0; i < arr.length; i++) {
            int j = Math.min(i + (int) (Math.random() * (K + 1)), arr.length - 1);
            if (!isSwap[i] && !isSwap[j]) {
                isSwap[i] = true;
                isSwap[j] = true;
                int tmp = arr[i];
                arr[i] = arr[j];
                arr[j] = tmp;
            }
        }
        return arr;
    }

    // for test
    public static int[] generateRandomArray(int maxSize, int maxValue) {
        // Math.random() -> [0,1)
        // Math.random() * N -> [0,N)
        // (int)(Math.random()*N) -> [0,N-1]
        int[] arr = new int[(int) (Math.random() * (maxSize + 1))];
        for (int i = 0; i < arr.length; i++) {
            // [-? , +?]
            arr[i] = (int) ((maxValue + 1) * Math.random()) - (int) ((maxValue + 1) * Math.random());
        }
        return arr;
    }

    public static int[] copyArray(int[] arr1) {
        if (arr1 == null) {
            return null;
        }
        int[] arr2 = new int[arr1.length];
        System.arraycopy(arr1, 0, arr2, 0, arr1.length);
        return arr2;
    }

    public static boolean isEqual(Integer o1, Integer o2) {
        if (o1 == null && o2 != null) {
            return false;
        }
        if (o1 != null && o2 == null) {
            return false;
        }
        if (o1 == null) {
            return true;
        }
        return o1.equals(o2);
    }
}