【LEETCODE】54、数组分类，简单级别，题目：605、532

数组类，简单级别完结。。。。

不容易啊，基本都是靠百度答案。。。。

希望做过之后后面可以自己复习，自己学会这个解法

package y2019.Algorithm.array;

/**
 * @ProjectName: cutter-point
 * @Package: y2019.Algorithm.array
 * @ClassName: CanPlaceFlowers
 * @Author: xiaof
 * @Description: TODO 605. Can Place Flowers
 * Suppose you have a long flowerbed in which some of the plots are planted and some are not.
 * However, flowers cannot be planted in adjacent plots - they would compete for water and both would die.
 * Given a flowerbed (represented as an array containing 0 and 1, where 0 means empty and 1 means not empty),
 * and a number n, return if n new flowers can be planted in it without violating the no-adjacent-flowers rule.
 *
 * 假设你有一个很长的花坛，一部分地块种植了花，另一部分却没有。可是，花卉不能种植在相邻的地块上，它们会争夺水源，两者都会死去。
 * 给定一个花坛（表示为一个数组包含0和1，其中0表示没种植花，1表示种植了花），和一个数 n 。能否在不打破种植规则的情况下种入 n 朵花？能则返回True，不能则返回False。
 * 来源：力扣（LeetCode）
 * 链接：https://leetcode-cn.com/problems/can-place-flowers
 * 著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。
 *
 * Input: flowerbed = [1,0,0,0,1], n = 1
 * Output: True
 * @Date: 2019/7/12 8:55
 * @Version: 1.0
 */
public class CanPlaceFlowers {

    public boolean solution(int[] flowerbed, int n) {
        //判断每个花之间要有空格
        int count = 0;
        for(int i = 0; i < flowerbed.length && count < n; ++i) {
            //判断是否是空的
            if(flowerbed[i] == 0) {
                //判断左右是否间隔1一个空位
                int pre = i == 0 ? 0 : flowerbed[i - 1];
                int next = i < flowerbed.length - 1 ? flowerbed[i + 1] : 0;
                if(pre == 0 && next == 0) {
                    ++count;
                    flowerbed[i] = 1;
                }
            }
        }

        if(count == n) {
            return true;
        } else {
            return false;
        }
    }

    public static void main(String args[]) {
        String as[] = {"bella","label","roller"};
        int[] A = {1,0,0,0,1};
        int k = 1;
        CanPlaceFlowers fuc = new CanPlaceFlowers();
        System.out.println(fuc.solution(A, k));
    }
}

 

package y2019.Algorithm.array;

import java.util.HashMap;
import java.util.Map;

/**
 * @ProjectName: cutter-point
 * @Package: y2019.Algorithm.array
 * @ClassName: FindPairs
 * @Author: xiaof
 * @Description: 532. K-diff Pairs in an Array
 * Given an array of integers and an integer k, you need to find the number of unique k-diff pairs in the array.
 * Here a k-diff pair is defined as an integer pair (i, j), where i and j are both numbers in the array and their absolute difference is k.
 *
 * Input: [3, 1, 4, 1, 5], k = 2
 * Output: 2
 * Explanation: There are two 2-diff pairs in the array, (1, 3) and (3, 5).
 * Although we have two 1s in the input, we should only return the number of unique pairs.
 *
 * 给定一个整数数组和一个整数 k, 你需要在数组里找到不同的 k-diff 数对。这里将 k-diff 数对定义为一个整数对 (i, j),
 * 其中 i 和 j 都是数组中的数字，且两数之差的绝对值是 k.
 *
 * 来源：力扣（LeetCode）
 * 链接：https://leetcode-cn.com/problems/k-diff-pairs-in-an-array
 * 著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。
 *
 * @Date: 2019/7/12 9:33
 * @Version: 1.0
 */
public class FindPairs {

    public int solution(int[] nums, int k) {

        if(k < 0) {
            return 0;
        }

        //这题用类似hash的方式
        Map<Integer, Integer> numMap = new HashMap();
        for(int t : nums) {
            if(!numMap.containsKey(t)) {
                numMap.put(t, 0);
            }
            //出现次数
            numMap.put(t, numMap.get(t) + 1);
        }
        //遍历查询缺失的一般
        int count = 0;
        //根据map中的数据进行判断，并且进行了去重
        for(Map.Entry entry : numMap.entrySet()) {
            //判断map中是否包含差值的数据，如果包含，还要避免是同同一对数据,剩余的个数要不能为0
            if(k == 0) {
                //特殊处理K为0的情况
                if((int) entry.getValue() >= 2) {
                    ++count;
                }
            } else if(numMap.containsKey((int) entry.getKey() + k)) {//因为是递增的，所以可以吧相同对排除掉
                ++count;
            }
        }

        return count;
    }

    public static void main(String args[]) {
        int[] A = {3,1,4,1,5};
        int[] B = {1,2,3,4,5};
        int k = -1;
        FindPairs fuc = new FindPairs();
        System.out.println(fuc.solution(A, k));
    }
}