区间问题
区间问题
1. 缩
LeetCode：452. 用最少数量的箭引爆气球
class Solution {
public int findMinArrowShots(int[][] points) {
int res = 0;
List<Point> list = new ArrayList<>();
for (int[] point : points) {
list.add(new Point(point[0], point[1]));
}
Collections.sort(list, new Comparator<Point>() {
@Override
public int compare(Point o1, Point o2) {
if (o1.left != o2.left){
return Long.compare(o1.left, o2.left);
}
return Long.compare(o1.right, o2.right);
}
});
for (int i = 0; i < list.size(); i++) {
Point point = list.get(i);
res++;
while (i + 1 < list.size() && point.right >= list.get(i + 1).left){ // 尽量去缩进
point.right = Math.min(point.right, list.get(i + 1).right);
i++;
}
}
return res;
}
}
class Point{
long left;
long right;
public Point(long left, long right) {
this.left = left;
this.right = right;
}
}
435. 无重叠区间
class Solution {
public int eraseOverlapIntervals(int[][] intervals) {
ArrayList<Point> list = new ArrayList<>();
for (int[] interval : intervals) {
list.add(new Point(interval[0], interval[1]));
}
Collections.sort(list, new Comparator<Point>() {
@Override
public int compare(Point o1, Point o2) {
if (o1.left != o2.left){
return o1.left - o2.left;
}
return o1.right - o2.right;
}
});
int res = 0;
for (int i = 0; i < list.size(); i++) {
Point point = list.get(i);
while (i + 1 < list.size() && point.right > list.get(i + 1).left){
res++;
point.right = Math.min(point.right, list.get(i + 1).right);
i++;
}
}
return res;
}
}
class Point{
int left;
int right;
public Point(int left, int right) {
this.left = left;
this.right = right;
}
}
OD 文艺表演
package com.llq.oo;
import java.util.*;
/**
* @Author: Ronnie LEE
* @Date: 2023/9/28 - 09 - 28 - 15:47
* @Description: com.llq.oo
* @version: 1.0
*/
public class show {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int count = Integer.parseInt(in.nextLine());
List<Point> list = new ArrayList<>();
for (int i = 0; i < count; i++) {
int start = in.nextInt();
int duration = in.nextInt();
list.add(new Point(start, start + duration + 15));
}
for (Point point : list) {
System.out.println(point.left + " " + point.right);
}
Collections.sort(list, new Comparator<Point>() {
@Override
public int compare(Point o1, Point o2) {
if (o1.left < o2.left){
return o1.left - o2.left;
}
return o1.right - o2.right;
}
});
int res = 0;
for (int i = 0; i < list.size(); i++) {
res++;
Point point = list.get(i);
while (i + 1 < list.size() && point.right > list.get(i + 1).left){
point.right = Math.min(point.right, list.get(i + 1).right);
i++;
}
}
System.out.println(res);
}
}
class Point{
int left;
int right;
public Point(int left, int right) {
this.left = left;
this.right = right;
}
}
2. 扩
OD：185. 路灯照明问题
难点：控制左右界
- 左：>= 0
- 右：(count - 1) * 100;
import java.util.Scanner;
import java.util.*;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
static List<Tree> res = new ArrayList<>();
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int count = Integer.parseInt(in.nextLine());
int RLen = (count - 1) * 100;
List<Tree> trees = new ArrayList<>();
for (int i = 0; i < count; i++) {
long temp = in.nextLong();
long left = Math.max(100 * i - temp, 0);
long right = Math.min(100 * i + temp, RLen);
trees.add(new Tree(left, right));
}
Collections.sort(trees, (o1, o2) -> {
if (o1.left != o2.left){
return Long.compare(o1.left, o2.left);
}
return Long.compare(o1.right, o2.right);
});
long sum = (count - 1) * 100;
for (int i = 0; i < trees.size(); i++) {
Tree tree = trees.get(i);
while (i + 1 < trees.size() && tree.right >= trees.get(i + 1).left){
tree.right = Math.max(tree.right, trees.get(i + 1).right);
i++;
}
sum -= tree.right - tree.left;
}
System.out.println(sum);
}
}
class Tree{
long left;
long right;
public Tree(long left, long right) {
this.left = left;
this.right = right;
}
}
3. 先缩再扩
OD230：区间交集
import java.util.Scanner;
import java.util.*;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
static List<Num> res = new ArrayList<>();
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
List<Num> list = new ArrayList<>();
int count = Integer.parseInt(in.nextLine());
for (int i = 0; i < count; i++) {
int a = in.nextInt();
int b = in.nextInt();
list.add(new Num(a, b));
}
Collections.sort(list, (o1, o2) -> o1.left - o2.left);
for (int i = 0; i < list.size(); i++) {
Num num = list.get(i);
for (int j = i + 1; j < list.size(); j++) {
Num num1 = list.get(j);
if (num.right >= num1.left){
isCommon(list.get(i), list.get(j));
}else {
break;
}
}
}
if (res.size() == 0){
System.out.println("None");
return;
}
Collections.sort(res, (o1, o2) -> o1.left - o2.left);
for (int i = 0; i < res.size(); i++) {
Num now = res.get(i);
while (i + 1 < res.size() && res.get(i + 1).left <= now.right){
now.right = Math.max(now.right, res.get(i + 1).right);
i++;
}
System.out.println(now.left + " " + now.right);
}
}
public static void isCommon(Num num1, Num num2){
int left = Math.max(num1.left, num2.left);
int right = Math.min(num1.right, num2.right);
res.add(new Num(left,right));
}
}
class Num {
int left;
int right;
public Num(int left, int right) {
this.left = left;
this.right = right;
}
}
