package 排序;
import java.util.Scanner;
public class 快速排序 {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner 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
java复制代码
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 stub
Scanner 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
java复制代码
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1
int l = 1,r = 1,mid;
while(l<r) {
mid = (l+r)/2;
if(check(mid)) r = mid;
else l = mid+1;
}
// 模板1
while(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
java复制代码
package 二分;
public class 浮点二分___平方根 {
public static void main(String[] args) {
// TODO Auto-generated method stub
int 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);
}
}