笔试算法题目,奶牛排队喝水

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import java.util.*;
/**
 * Created by Daxin on 2017/8/19.
 * <p/>
 * 奶牛排队饮水问题
 * 输入:n牛的数目,然后n个整数表示牛的序号
 * 输出:输出交换最少次数
 * <p/>
 * 例如一个测试用例:9<br>
 * 2,2,1,3,3,3,2,3,1<br>
 * 输出:4
 *
 *在线题目地址:http://www.hustoj.com/oj/problem.php?id=1056
 *
 *
 */
public class CattleSortWater {
    public static void main(String[] args) {
//        int[] nums = {2, 2, 1, 3, 3, 3, 2, 3, 1};
        Scanner cin = new Scanner(System.in);
        int n = cin.nextInt();
        int[] nums = new int[n];
        for (int i = 0; i < n; i++) {
            nums[i] = cin.nextInt();
        }
        System.out.println(solve(nums));
//        System.out.println(Arrays.toString(nums));
    }
    public static int solve(int[] nums) {
        int result = 0;
        Map<Integer, Integer> wcount = new TreeMap<>();
        Map<Integer, Integer> range = new TreeMap<>();
        for (int num : nums) {
            Integer tmp = wcount.get(num);
            wcount.put(num, tmp == null 1 : tmp + 1);
        }
        Set<Integer> set = wcount.keySet();
        int pre = 0;
        for (int i : set) {
            int tmp = wcount.get(i) + pre;
            range.put(i, tmp);
            pre = tmp;
        }
        for (int num : set) {
            int times = wcount.get(num);
            int ran = range.get(num);
            for (int i = ran - 1, t = times; t > 0; t--, i--) {
                if (nums[i] != num) {
                    int r = get(nums, range.get(nums[i]), wcount.get(nums[i]), num);
                    if (r != -1) { //在nums[i] 区间中寻找到了num
                        int tmp = nums[r];
                        nums[r] = nums[i];
                        nums[i] = tmp;
                        result++;
                    else {// 在希望区间没有找到,进行余下遇见全扫描
                        int rr = getRange(nums, ran, num,range.get(nums[i])-wcount.get(nums[i]),range.get(nums[i]));
                        if (rr != -1) {
                            int tmp = nums[rr];
                            nums[rr] = nums[i];
                            nums[i] = tmp;
                            result++;
                        }
                    }
                }
            }
        }
        return result;
    }
    /**
     *
     * @param nums 数组
     * @param range 结束的下标
     * @param times 出现的次数,range-times就是起始下标
     * @param expect 希望查找的希望值
     * @return
     */
    public static int get(int[] nums, int range, int times, int expect) {
        for (int i = range - 1, t = times; t > 0; t--, i--) {
            if (nums[i] == expect) {
                return i;
            }
        }
        return -1;
    }
    /**
     *
     * @param nums 数组
     * @param start 查找的起始位置,结束位置是数组的结束
     * @param expect 期望寻找到的值
     * @param exceptStart 排除区域的起始下标
     * @param exceptEnd 排除区域的结束下标
     * @return 返回下标
     */
    public static int getRange(int[] nums, int start, int expect,int exceptStart,int exceptEnd) {
        for (; start < nums.length; start++) {
            if(start>=exceptStart&&start<exceptEnd)
                continue;
            if (nums[start] == expect) {
                return start;
            }
        }
        return -1;
    }
}

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