一、排序

1.1 快速排序

package 排序;import java.util.Scanner;public class 快速排序 {public static void main(String[] args) {// TODO Auto-generated method stubScanner scan = new Scanner(System.in);int []a = new int[110];int n = scan.nextInt();for(int i=0;i<n;i++)a[i] = scan.nextInt();Q_sort(a,0,n-1);for(int i=0;i<n;i++)System.out.print(a[i]+" ");}static void Q_sort(int a[],int l,int r) {if(l>=r) return;int x = a[l];int i = l - 1;int j = r + 1;while(i<j) {do i++; while(a[i]<x);do j--; while(a[j]>x);if(i<j) {int t = a[i];a[i] = a[j];a[j] = t;}}Q_sort(a,l,j);Q_sort(a,j+1,r);}
}

1.2 归并排序

package 排序;
import java.util.*;
public class 归并排序 {static int []tmp = new int[110];	//辅助数组public static void main(String[] args) {// TODO Auto-generated method stubScanner scan = new Scanner(System.in);int []a = new int[110];int n = scan.nextInt();for(int i=0;i<n;i++)a[i] = scan.nextInt();Merge_sort(a,0,n-1);for(int i=0;i<n;i++)System.out.print(a[i]+" ");}static void Merge_sort(int []a,int l,int r) {// 递归退出条件if(l>=r)	return;// 分int mid =  l + r >> 1;Merge_sort(a,l,mid);Merge_sort(a,mid+1,r);// 合int ans=0,x=l,y=mid+1;while(x<=mid&&y<=r)if(a[x]<=a[y])	tmp[ans++] = a[x++];else  tmp[ans++] = a[y++];while(x<=mid) tmp[ans++] = a[x++];while(y<=r) tmp[ans++] = a[y++];for(int i=l,pos=0;i<=r;i++) a[i] = tmp[pos++];}
}

二、二分

2.1 整数二分

package 二分;
import java.util.*;
public class 整数二分 {public static void main(String[] args) {// TODO Auto-generated method stub// 模板1int l = 1,r = 1,mid;while(l<r) {mid = (l+r)/2;if(check(mid)) r = mid;else l = mid+1;}// 模板1while(l<r) {mid = (l+r+1)/2;if(check(mid)) l = mid;else r = mid-1;}}static boolean check(int x) {return true;}
}

2.2 浮点二分

package 二分;public class 浮点二分___平方根 {public static void main(String[] args) {// TODO Auto-generated method stubint x =4;double l = 0,r = x;while((r-l) > 1e-8) {double mid = (l+r)/2;if(mid*mid>=x) r = mid;else l = mid;}System.out.print(l);}
}