Day35 贪心 part04

860.柠檬水找零

我的思路:
只要逐个考虑bills数组可能的数字 5/10/20，分别考虑

解答：

class Solution {public boolean lemonadeChange(int[] bills) {int fivecount = 0;int tencount = 0;for(int bill : bills) {if(bill == 5) {fivecount++;}else if(bill == 10) {if(fivecount <= 0) {return false;}fivecount --;tencount ++;}else {if(fivecount > 0 && tencount > 0) {fivecount --;tencount --;}else if(fivecount >= 3) {fivecount -= 3;}else {return false;}}}return true;}
}

406.根据身高重建队列

我的思路：
类似分糖果，people[i] = [hi, ki] 如果身高h相同，k按照从小到大排序，否则按照身高h从高到低排序

解答：

class Solution {public int[][] reconstructQueue(int[][] people) {ArrayList<int[] > list = new ArrayList<>();Arrays.sort(people, (a, b) -> a[0] == b[0] ? a[1] - b[1] : b[0] - a[0]);for(int[] person : people) {list.add(person[1], person);}int[][] res = new int[people.length][2];for(int i = 0; i < people.length; i ++) {res[i] = list.get(i);}return res;}
}

452. 用最少数量的箭引爆气球

我的思路：
需要注意的是，对point进行排序的时候，是按end值进行从小到大排序

解答：

class Solution {public int findMinArrowShots(int[][] points) {Arrays.sort(points, (a, b) -> Integer.compare(a[1], b[1]));int arrow = 1;int end = points[0][1];for(int i = 0; i < points.length; i ++) {if(points[i][0] > end) {arrow ++;end = points[i][1];}}return arrow;}
}