Android LeetCode Happy Number 解題

動動腦，不會老
題目： https://leetcode.com/problems/happy-number/

Write an algorithm to determine if a number is "happy".

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

Example: 19 is a happy number

• 12 + 92 = 82
• 82 + 22 = 68
• 62 + 82 = 100
• 12 + 02 + 02 = 1

用Android app試著做一個

1./res/layout/main.xml

2.MainActivity.java

package tw.android;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class Main extends Activity {

 private EditText etNumber;
 private Button btSend;
 private TextView tvInfo;

 private int[] numberArray;

 /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);

  etNumber = (EditText) findViewById(R.id.etNumber);
  btSend = (Button) findViewById(R.id.btSend);
  tvInfo = (TextView) findViewById(R.id.tvInfo);

  btSend.setOnClickListener(new Button.OnClickListener() {
   public void onClick(View v) {
    int number = Integer.parseInt(etNumber.getText().toString()); // 輸入數字
    if (isHappy(number)) {
     tvInfo.setText(number + "是 Happy Number");
    } else {
     tvInfo.setText(number + "不是 Happy Number");
    }

   }
  });

 }

 /*
  * Write an algorithm to determine if a number is "happy".
  * 
  * A happy number is a number defined by the following process: Starting
  * with any positive integer, replace the number by the sum of the squares
  * of its digits, and repeat the process until the number equals 1 (where it
  * will stay), or it loops endlessly in a cycle which does not include 1.
  * Those numbers for which this process ends in 1 are happy numbers.
  * 
  * Example: 19 is a happy number
  * 
  * 1^2 + 9^2 = 82 
  * 8^2 + 2^2 = 68 
  * 6^2 + 8^2 = 100 
  * 1^2 + 0^2 + 0^2 = 1
  */

 /* 回傳驗證是否為happy number */
 public boolean isHappy(int n) {
  Log.i("keyNumber:", n + "");
  int sum, length;
  do {
   sum = getNumber(n, Integer.toString(n).length());
   length = Integer.toString(sum).length(); // 總和數字長度
   n = sum;
  } while (length != 1);// 重複執行到剩個位數
  
  Log.i("sum:", sum + "");
  if (sum == 1) { // 個位數等於1 happy number!!
   return true;
  } else { // 不是happy number...
   return false;
  }
 }

 /* 取得每個數字 放入數字陣列 計算總合 */
 public int getNumber(int n, int length) {
  /* 建立每個數字陣列 */
  numberArray = new int[length];
  int quotient = 0;// 商數
  int sum = 0; // 總合
  for (int i = 0; i < length; i++) {
   if (i == 0) { // 一開始輸入的數字計算
    numberArray[i] = n % 10; // 獲得餘數
    quotient = n / 10; // 獲得商數
   } else { // 計算後的總合再計算
    numberArray[i] = quotient % 10; // 獲得餘數
    quotient = quotient / 10; // 獲得商數
   }
   sum += (int) Math.pow(numberArray[i], 2); // 計算總和

  }
  return sum; // 回傳總和
 }

}

檔案下載:https://github.com/terryyamg/HappyNumberTest