Java 将两个十进制整数与除法运算相乘
我试着将两个数相乘,它们是正整数,它们的位数相同,通过递归的分治,我试着这样做:T(n)=4T(n/2)+O(n) 注意:我知道它以θ(n^2)运行,这很糟糕!这对我来说只是一种锻炼。 谢谢你,很抱歉我的英语不好。:) 我的问题是:我的错误在哪里? 代码如下:Java 将两个十进制整数与除法运算相乘,java,divide-and-conquer,multiplication,Java,Divide And Conquer,Multiplication,我试着将两个数相乘,它们是正整数,它们的位数相同,通过递归的分治,我试着这样做:T(n)=4T(n/2)+O(n) 注意:我知道它以θ(n^2)运行,这很糟糕!这对我来说只是一种锻炼。 谢谢你,很抱歉我的英语不好。:) 我的问题是:我的错误在哪里? 代码如下: import java.util.Scanner; public class main { static int res=0; static int stage =0; public static void main(String[] a
import java.util.Scanner;
public class main {
static int res=0;
static int stage =0;
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
char[] Num1;
char[] Num2;
String num1 = in.nextLine();
String num2 = in.nextLine();
in.close();
Num1 = num1.toCharArray();
Num2 = num2.toCharArray();
DaQMultiplay(Num1, Num2);
System.out.println(res);
}
static int DaQMultiplay(char[] num1,char[] num2){
if(num1.length<2){
stage++;
int num1sd =Integer.parseInt(new String(num1));
int num2sd =Integer.parseInt(new String(num2));
return (num1sd*num2sd);
}
stage++;
double len = num1.length;
int lenl = (int) Math.ceil(len/2);
char []ln1 = new char[lenl];
char []rn1 = new char[(int) (len-lenl)];
char []ln2 = new char[lenl];
char []rn2 = new char[(int) (len-lenl)];
for (int i = 0; i < ln1.length; i++) {
ln1[i]=num1[i];
}
for (int i = 0; i < rn1.length; i++) {
rn1[i]=num1[i+lenl];
}
for (int i = 0; i < ln2.length; i++) {
ln2[i]=num2[i];
}
for (int i = 0; i < rn2.length; i++) {
rn2[i]=num2[i+lenl];
}
System.out.print("Left Side of num1:"+stage+" ");
System.out.println(ln1);
System.out.print("Right Side of num1:"+stage+" ");
System.out.println(rn1);
System.out.print("Left Side of num2:"+stage+" ");
System.out.println(ln2);
System.out.print("Right Side of num2:"+stage+" ");
System.out.println(rn2);
res+=DaQMultiplay(ln1,ln2)*(10^((int)len));
System.out.println("res: "+res);
res+=DaQMultiplay(ln1,rn2)*10^((int) (len-lenl));
System.out.println("res: "+res);
res+=DaQMultiplay(rn1,ln2)*10^((int) (len-lenl));
System.out.println("res: "+res);
res+=DaQMultiplay(rn1, rn2);
System.out.println("res: "+res);
return 0;
}
}
通常,您的代码不会处理num2解析为num1之前的一位数的情况。这将导致通过DaQ方法生成一个空字符串,最终引发异常。首先需要添加对num2解析处理的检查。此检查解决了第一个异常(第46行附近):
我不确定第二次检查是否适合您编写的算法,但总体思路是,这条if语句
if(num1.length这是完整的程序,一切正常:
import java.io.ObjectInputStream.GetField;
import java.util.Scanner;
public class main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
char[] Num1;
char[] Num2;
String num1 = in.nextLine();
String num2 = in.nextLine();
in.close();
Num1 = num1.toCharArray();
Num2 = num2.toCharArray();
check(Num1, Num2);
}
static int DaQMultiplay(char[] num1,char[] num2){
int res=0;
if(num1.length<=1){
int num1sd = 0;
int num2sd = 0;
if(num1!=null && !num1.equals("") && new String(num2).trim().length()>0){
num1sd =Integer.parseInt(new String(num1));
}
if(num2!=null && !num2.equals("") && new String(num2).trim().length()>0){
num2sd=Integer.parseInt(new String(num2));
}
return (num1sd*num2sd);
}
double len = num1.length;
int lenl = (int) Math.ceil(len/2);
char []ln1 = new char[lenl];
char []rn1 = new char[(int) (len-lenl)];
char []ln2 = new char[lenl];
char []rn2 = new char[(int) (len-lenl)];
for (int i = 0; i < ln1.length; i++) {
ln1[i]=num1[i];
}
for (int i = 0; i < rn1.length; i++) {
rn1[i]=num1[i+lenl];
}
for (int i = 0; i < ln2.length; i++) {
ln2[i]=num2[i];
}
for (int i = 0; i < rn2.length; i++) {
if(num2.length>i+lenl){
rn2[i]=num2[i+lenl];
}
}
res+=(DaQMultiplay(ln1,ln2)*(Math.pow(10, len)));
res+=(DaQMultiplay(rn1,ln2)*(Math.pow(10, (len/2))));
res+=(DaQMultiplay(ln1,rn2)*(Math.pow(10, (len/2))));
res+=(DaQMultiplay(rn1, rn2));
return res;
}
static void check(char []Num1,char []Num2){
int res=0;
if ((Num1.length%2)==0) {
res=DaQMultiplay(Num1, Num2);
System.out.println(res);
}
else{
String num1 = String.valueOf(Num1);
num1 = num1+"0";
String num2 = String.valueOf(Num2);
num2 = num2+"0";
Num1=num1.toCharArray();
Num2=num2.toCharArray();
res=DaQMultiplay(Num1, Num2);
res=(res/100);
System.out.println(res);
}
}
}
import java.io.ObjectInputStream.GetField;
导入java.util.Scanner;
公共班机{
公共静态void main(字符串[]args){
扫描仪输入=新扫描仪(系统输入);
char[]Num1;
char[]Num2;
字符串num1=in.nextLine();
字符串num2=in.nextLine();
in.close();
Num1=Num1.toCharArray();
Num2=Num2.toCharArray();
检查(Num1,Num2);
}
静态int-DaQMultiplay(char[]num1,char[]num2){
int res=0;
如果(num1.长度0){
num1sd=Integer.parseInt(新字符串(num1));
}
if(num2!=null&&!num2.equals(“”&&新字符串(num2.trim().length()>0){
num2sd=Integer.parseInt(新字符串(num2));
}
返回(num1sd*num2sd);
}
双透镜=num1.5长度;
int lenl=(int)Math.ceil(len/2);
char[]ln1=新字符[lenl];
char[]rn1=新字符[(int)(len lenl)];
char[]ln2=新字符[lenl];
char[]rn2=新字符[(int)(len lenl)];
对于(int i=0;ii+lenl){
rn2[i]=num2[i+lenl];
}
}
res+=(DaQMultiplay(ln1,ln2)*(Math.pow(10,len));
res+=(DaQMultiplay(rn1,ln2)*(Math.pow(10,(len/2)));
res+=(DaQMultiplay(ln1,rn2)*(Math.pow(10,(len/2)));
res+=(DaQMultiplay(rn1,rn2));
返回res;
}
静态无效检查(字符[]Num1,字符[]Num2){
int res=0;
如果((Num1.长度%2)==0){
res=DaQMultiplay(Num1,Num2);
系统输出打印项次(res);
}
否则{
String num1=String.valueOf(num1);
num1=num1+“0”;
String num2=String.valueOf(num2);
num2=num2+“0”;
Num1=Num1.toCharArray();
Num2=Num2.toCharArray();
res=DaQMultiplay(Num1,Num2);
res=(res/100);
系统输出打印项次(res);
}
}
}
谢谢,它解决了错误,但在征服步骤中算法的正确性仍然存在问题,我不知道如何处理4个传入的递归尾部,我的算法基于此文档:
for (int i = 0; i < rn2.length; i++) {
if(num2.length>i+lenl){
rn2[i]=num2[i+lenl];
}
}
if(num1!=null && !num1.equals("") && new String(num2).trim().length()>0){
num1sd =Integer.parseInt(new String(num1));
}
if(num2!=null && !num2.equals("") && new String(num2).trim().length()>0){
num2sd=Integer.parseInt(new String(num2));
}
import java.util.Scanner;
public class main {
static int res=0;
static int pow;
static int stage =0;
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
char[] Num1;
char[] Num2;
String num1 = in.nextLine();
String num2 = in.nextLine();
in.close();
Num1 = num1.toCharArray();
Num2 = num2.toCharArray();
pow = Num1.length;
DaQMultiplay(Num1, Num2);
System.out.println(res);
}
static int DaQMultiplay(char[] num1,char[] num2){
if(num1.length<2){
stage++;
int num1sd = 0;
int num2sd = 0;
if(num1!=null && !num1.equals("") && new String(num2).trim().length()>0){
num1sd =Integer.parseInt(new String(num1));
}
if(num2!=null && !num2.equals("") && new String(num2).trim().length()>0){
num2sd=Integer.parseInt(new String(num2));
}
return (num1sd*num2sd);
}
stage++;
double len = num1.length;
int lenl = (int) Math.ceil(len/2);
char []ln1 = new char[lenl];
char []rn1 = new char[(int) (len-lenl)];
char []ln2 = new char[lenl];
char []rn2 = new char[(int) (len-lenl)];
for (int i = 0; i < ln1.length; i++) {
ln1[i]=num1[i];
}
for (int i = 0; i < rn1.length; i++) {
rn1[i]=num1[i+lenl];
}
for (int i = 0; i < ln2.length; i++) {
ln2[i]=num2[i];
}
for (int i = 0; i < rn2.length; i++) {
if(num2.length>i+lenl){
rn2[i]=num2[i+lenl];
}
}
System.out.print("Left Side of num1:"+stage+" ");
System.out.println(ln1);
System.out.print("Right Side of num1:"+stage+" ");
System.out.println(rn1);
System.out.print("Left Side of num2:"+stage+" ");
System.out.println(ln2);
System.out.print("Right Side of num2:"+stage+" ");
System.out.println(rn2);
res+=(DaQMultiplay(ln1,ln2)*(Math.pow(10, len)));
System.out.println(res);
res+=(DaQMultiplay(rn1,ln2)*(Math.pow(10, (len/2))));
System.out.println(res);
res+=(DaQMultiplay(ln1,rn2)*(Math.pow(10, (len/2))));
System.out.println(res);
res+=(DaQMultiplay(rn1, rn2));
System.out.println(res);
return 0;
}
}
20011
91281
Left Side of num1:1 200
Right Side of num1:1 11
Left Side of num2:1 912
Right Side of num2:1 81
Left Side of num1:2 20
Right Side of num1:2 0
Left Side of num2:2 91
Right Side of num2:2 2
Left Side of num1:3 2
Right Side of num1:3 0
Left Side of num2:3 9
Right Side of num2:3 1
1800
1800
1820
1820
0
0
Left Side of num1:9 2
Right Side of num1:9 0
Left Side of num2:9 2
Right Side of num2:9
import java.io.ObjectInputStream.GetField;
import java.util.Scanner;
public class main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
char[] Num1;
char[] Num2;
String num1 = in.nextLine();
String num2 = in.nextLine();
in.close();
Num1 = num1.toCharArray();
Num2 = num2.toCharArray();
check(Num1, Num2);
}
static int DaQMultiplay(char[] num1,char[] num2){
int res=0;
if(num1.length<=1){
int num1sd = 0;
int num2sd = 0;
if(num1!=null && !num1.equals("") && new String(num2).trim().length()>0){
num1sd =Integer.parseInt(new String(num1));
}
if(num2!=null && !num2.equals("") && new String(num2).trim().length()>0){
num2sd=Integer.parseInt(new String(num2));
}
return (num1sd*num2sd);
}
double len = num1.length;
int lenl = (int) Math.ceil(len/2);
char []ln1 = new char[lenl];
char []rn1 = new char[(int) (len-lenl)];
char []ln2 = new char[lenl];
char []rn2 = new char[(int) (len-lenl)];
for (int i = 0; i < ln1.length; i++) {
ln1[i]=num1[i];
}
for (int i = 0; i < rn1.length; i++) {
rn1[i]=num1[i+lenl];
}
for (int i = 0; i < ln2.length; i++) {
ln2[i]=num2[i];
}
for (int i = 0; i < rn2.length; i++) {
if(num2.length>i+lenl){
rn2[i]=num2[i+lenl];
}
}
res+=(DaQMultiplay(ln1,ln2)*(Math.pow(10, len)));
res+=(DaQMultiplay(rn1,ln2)*(Math.pow(10, (len/2))));
res+=(DaQMultiplay(ln1,rn2)*(Math.pow(10, (len/2))));
res+=(DaQMultiplay(rn1, rn2));
return res;
}
static void check(char []Num1,char []Num2){
int res=0;
if ((Num1.length%2)==0) {
res=DaQMultiplay(Num1, Num2);
System.out.println(res);
}
else{
String num1 = String.valueOf(Num1);
num1 = num1+"0";
String num2 = String.valueOf(Num2);
num2 = num2+"0";
Num1=num1.toCharArray();
Num2=num2.toCharArray();
res=DaQMultiplay(Num1, Num2);
res=(res/100);
System.out.println(res);
}
}
}