基本算法demo

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//布局
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    tools:context="com.bwie.number.MainActivity">    <ScrollView        android:layout_width="match_parent"        android:layout_height="match_parent">        <LinearLayout            android:orientation="vertical"            android:layout_width="match_parent"            android:layout_height="match_parent">            <EditText                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:id="@+id/num"                android:hint="输入阶乘数"                />            <Button                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:id="@+id/start"                android:text="开始阶乘"                />            <TextView                android:id="@+id/textname"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:text="Hello World!" />            <TextView                android:id="@+id/textname1"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:text="Hello World!" />            <TextView                android:id="@+id/textname2"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:text="Hello World!" />            <TextView                android:id="@+id/textname3"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:text="Hello World!" />            <TextView                android:id="@+id/textname4"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:text="Hello World!" />            <TextView                android:id="@+id/textname5"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:text="Hello World!" />            <TextView                android:id="@+id/textname6"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:text="Hello World!" />        </LinearLayout>    </ScrollView></LinearLayout>//主要代码 package com.bwie.number;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.TextView;import java.math.BigInteger;import java.util.ArrayList;import java.util.Random;public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        final EditText editText = findViewById(R.id.num);        Button button = findViewById(R.id.start);        TextView textView = findViewById(R.id.textname);        TextView textView1 = findViewById(R.id.textname1);        final TextView textView2 = findViewById(R.id.textname2);        TextView textView3 = findViewById(R.id.textname3);        TextView textView4 = findViewById(R.id.textname4);        TextView textView5 = findViewById(R.id.textname5);        TextView textView6 = findViewById(R.id.textname6);        TextView textView7 = findViewById(R.id.textname7);        TextView textView8 = findViewById(R.id.textname8);        textView.setText("0.杨辉三角\n" + get(1, 5));        textView1.setText("1.杨辉三角\n" + get(2, 8));        textView3.setText("3.递归10的阶乘：\n    " + digui(10));        textView4.setText("4.12个月后兔子对数:\n   " + feibo(12));        textView5.setText("5.无序的二维数组\n" + erwei(4, 0));        textView6.setText("6.行有序的二维数组\n" + erwei(4, 1));        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                String num=editText.getText().toString();                //textView2.setText("2.大数阶乘:\n" + digui(new BigInteger(num)));                textView2.setText("2.大数阶乘:\n"+jiecheng(Integer.parseInt(num)));            }        });    }    //二维数组    public String erwei(int num, int type) {        String a = "";        int[][] arr = new int[num][num];        for (int i = 0; i < num; i++) {            for (int j = 0; j < num; j++) {                Random rand = new Random();                int ran = rand.nextInt(num * num) + 1;                arr[i][j] = feibo(ran);            }        }        switch (type) {            case 0://无序                for (int i = 0; i < num; i++) {                    for (int j = 0; j < num; j++) {                        a += arr[i][j] + "  ";                    }                    a += "\n";                }                break;            case 1://行有序                for (int i = 0; i < num; i++) {                    for (int j = 0; j < num; j++) {                        int min = arr[i][j];                        for (int m = j; m < num; m++) {                            if (arr[i][m] < min) {                                min = arr[i][m];                                arr[i][m] = arr[i][j];                                arr[i][j] = min;                            }                        }                    }                }                for (int i = 0; i < num; i++) {                    for (int j = 0; j < num; j++) {                        a += arr[i][j] + "  ";                    }                    a += "\n";                }                break;        }        return a;    }    //递归    public int digui(int length) {        int num = length;        if (num == 1) {            return 1;        } else {            return num * digui(num - 1);        }    }    //递归2    public BigInteger digui(BigInteger length) {        BigInteger num = length;        BigInteger big1 = BigInteger.valueOf(1);        if (num.compareTo(big1) == 0) {            return big1;        } else {            return num.multiply(digui(num.subtract(big1)));        }    }    //大数阶乘    private BigInteger jiecheng(int n) {        BigInteger a=BigInteger.valueOf(n);        for (int i=1;i<=n;i++){            a = a.multiply(BigInteger.valueOf(i));        }        return a;    }    //斐波那契    public int feibo(int moth) {        ArrayList<Integer> list = new ArrayList<>();        for (int i = 1; i <= moth; i++) {            if (i == 1 || i == 2) {                list.add(i - 1, 1);            } else {                list.add(i - 1, list.get(i - 2) + list.get(i - 3));            }        }        return list.get(moth - 1);    }    //杨辉三角    public String get(int type, int count) {        String arr = "";        int num[][] = new int[count][count];//这个数组有几层        for (int i = 0; i < count; i++)//主要是对数组进行赋值        {            for (int j = 0; j <= i; j++)//每一层的个数都是小于等于层数的，m代表层数，n代表着第几个数            {                if (j == 0 || i == j)//每一层的开头都是1，i==n的时候也是1,必须要这个，凡事都得有个开头                {                    num[i][j] = 1;                } else                    num[i][j] = num[i - 1][j - 1] + num[i - 1][j];//这个就是递推的方法了，例如3=1+2，3的坐标就是3[3,1]=1[2,0]+2[2,1];            }        }        for (int i = 0; i < count; i++)//主要是输出数组        {            if (type == 1) {                for (int l = i; l < count; l++)//这个主要是打空格，好看一点，去掉就是直角三角形了                {                    arr = arr + "   ";                }            }            for (int j = count - i; j <= count; j++)//这个就是打印数组了，每层循环几次就几个            {                if (num[i][count - j] < 8 || i == 2) {                    arr = arr + num[i][count - j] + "    ";                } else {                    arr = arr + num[i][count - j] + "  ";                }            }            arr = arr + "\n";        }        return arr;    }}
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