数组的partition调整

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(reader.readLine());
        String[] str = reader.readLine().split(" ");
        reader.close();
        int[] arr = new int[n];
        for (int i = 0; i < n; ++i) {
            arr[i] = Integer.parseInt(str[i]);
        }
        leftUnique(arr, n);
        StringBuilder sb = new StringBuilder();
        for (int num : arr)
            sb.append(num).append(" ");
        System.out.println(sb.substring(0, sb.length() - 1));
    }

    private static void leftUnique(int[] arr,int n) {
        if (arr == null || arr.length < 2) {
            return;
        }
        int u = 0;
        int i = 1;
        while (i != n) {
            if (arr[i++] != arr[u]) {
                swap(arr, ++u, i - 1);
            }
        }
    }

    private static void swap(int[] arr, int i, int j) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }

}