F. Feed Cats
题目大意
给一长度为 在数轴上选取一些点作为特殊点 在满足 问最多能选多少个特殊点 解题思路
对于每个点有放或不放两种状态 考虑 若不放， 若放，则 两者取 最靠左的端点为 已经被填过的位置上值一定是比当前值小的，不用更新 package Tx;
import java.io.*;
import java.math.BigInteger;
import java.util.Arrays;
import java.util.BitSet;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Random;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.Vector;
public class Tx1{
static long md=(long)998244353;
static long Linf=Long.MAX_VALUE/2;
static int inf=Integer.MAX_VALUE/2;
static
class Node{
int l;
int r;
public Node(int L,int R) {
l=L;
r=R;
}
}
static
class BIT{
int size;
int[] tr;
public BIT(int n) {
size=n;
tr=new int[n+5];
}
int lowbit(int x) {
return x&-x;
}
void update(int x,int k) {
for(int i=x;i<=size;i+=lowbit(i)) {
tr[i]+=k;
}
}
int query(int x) {
int res=0;
for(int i=x;i>0;i-=lowbit(i)) {
res+=tr[i];
}
return res;
}
}
public static void main(String[] args) throws IOException{
AReader input=new AReader();
PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
int T=input.nextInt();
while(T>0){
int n=input.nextInt();
int m=input.nextInt();
Node[] a=new Node[m+1];
BIT Tp=new BIT(n);
for(int i=1;i<=m;++i) {
int x=input.nextInt();
int y=input.nextInt();
a[i]=new Node(x, y);//初始所有区间
Tp.update(x, 1);
Tp.update(y+1, -1);
}
Arrays.sort(a,1,m+1,(o1,o2)->{
if(o1.l==o2.l)return o2.r-o1.r;
else return o1.l-o2.l;
});
Node[] b=new Node[n+1];//只保留左端点能包含的最长区间
int cnt=0;
a[0]=new Node(0, 0);
for(int i=1;i<=m;++i) {
if(a[i].l==a[i-1].l) continue;
else {
cnt++;
b[cnt]=new Node(a[i].l, a[i].r);
}
}
int[] c=new int[n+1];//数轴上每一位能到的最左端点
int lhs=-1;//维护已经处理过的区间，处理过的位置不会再被更新
int rhs=-1;
for(int i=1;i<=cnt;++i) {
if(lhs==-1&&rhs==-1) {
lhs=b[i].l;
rhs=b[i].r;
for(int j=lhs;j<=rhs;++j)c[j]=b[i].l;
}else {
if(b[i].l<lhs) {
for(int j=b[i].l;j<lhs;++j) {
c[j]=b[i].l;
}
lhs=b[i].l;
}
if(b[i].r>rhs) {
for(int j=rhs+1;j<=b[i].r;++j) {
c[j]=b[i].l;
}
rhs=b[i].r;
}
}
}
long[] f=new long[n+1];
f[1]=Tp.query(1);
for(int i=2;i<=n;++i) {
f[i]=f[i-1];
int t=Tp.query(i);
if(t==0)continue;
f[i]=Math.max(f[i], f[c[i]-1]+t);
}
out.println(f[n]);
T--;
}
out.flush();
out.close();
}
//System.out.println();
//out.println();
static
class AReader{
BufferedReader bf;
StringTokenizer st;
BufferedWriter bw;
public AReader(){
bf=new BufferedReader(new InputStreamReader(System.in));
st=new StringTokenizer("");
bw=new BufferedWriter(new OutputStreamWriter(System.out));
}
public String nextLine() throws IOException{
return bf.readLine();
}
public String next() throws IOException{
while(!st.hasMoreTokens()){
st=new StringTokenizer(bf.readLine());
}
return st.nextToken();
}
public char nextChar() throws IOException{
//确定下一个token只有一个字符的时候再用
return next().charAt(0);
}
public int nextInt() throws IOException{
return Integer.parseInt(next());
}
public long nextLong() throws IOException{
return Long.parseLong(next());
}
public double nextDouble() throws IOException{
return Double.parseDouble(next());
}
public float nextFloat() throws IOException{
return Float.parseFloat(next());
}
public byte nextByte() throws IOException{
return Byte.parseByte(next());
}
public short nextShort() throws IOException{
return Short.parseShort(next());
}
public BigInteger nextBigInteger() throws IOException{
return new BigInteger(next());
}
public void println() throws IOException {
bw.newLine();
}
public void println(int[] arr) throws IOException{
for (int value : arr) {
bw.write(value + " ");
}
println();
}
public void println(int l, int r, int[] arr) throws IOException{
for (int i = l; i <= r; i ++) {
bw.write(arr[i] + " ");
}
println();
}
public void println(int a) throws IOException{
bw.write(String.valueOf(a));
bw.newLine();
}
public void print(int a) throws IOException{
bw.write(String.valueOf(a));
}
public void println(String a) throws IOException{
bw.write(a);
bw.newLine();
}
public void print(String a) throws IOException{
bw.write(a);
}
public void println(long a) throws IOException{
bw.write(String.valueOf(a));
bw.newLine();
}
public void print(long a) throws IOException{
bw.write(String.valueOf(a));
}
public void println(double a) throws IOException{
bw.write(String.valueOf(a));
bw.newLine();
}
public void print(double a) throws IOException{
bw.write(String.valueOf(a));
}
public void print(char a) throws IOException{
bw.write(String.valueOf(a));
}
public void println(char a) throws IOException{
bw.write(String.valueOf(a));
bw.newLine();
}
}
}
的数轴，
个区间
表示
位置可能放或不放的最优结果
表示有多少个区间含
，在包含
，则
位置的选取，可以由
