現(xiàn)有n個(gè)紅白藍(lán)三種不同顏色的小球，亂序排列在一起，請(qǐng)通過(guò)兩兩交換任意兩個(gè)球，使得從左至右，依次是一些紅球、一些白球、一些藍(lán)球。

public class DutchNationalFlag {

    private void swap(int[] a, int index1, int index2) {
        int temp = a[index1];
        a[index1] = a[index2];
        a[index2] = temp;
    }

    public void dutchNationalFlag(int[] a, int n) {
        //紅色游標(biāo)
        int left = 0;
        //藍(lán)色游標(biāo)
        int right = n - 1;
        //白色游標(biāo)
        int cur = 1;
        while (cur <= right) {
            if (a[cur] == 0) { //紅色
                swap(a, left, cur);
                left++;
            } else if (a[cur] == 1) { //白色
                cur++;
            } else { //藍(lán)色
                swap(a, cur, right);
                right--;
            }
        }
    }

    public static void main(String[] args) {
        int[] a = { 0, 1, 1, 2, 2, 2, 0, 0, 0, 1, 1 };
        DutchNationalFlag dFlag = new DutchNationalFlag();
        dFlag.dutchNationalFlag(a, a.length);
        for (int value : a) {
            System.out.print(value);
            System.out.print(" ");
        }
    }
}