package com.lyj.calculate;
import java.math.BigDecimal;



public class BigInteger {
	
	/**
	 * 
	 * @param number1数字1
	 * @param number2数字2
	 *大整数相乘优化了
	 *     
	 * @return
	 */
	public static String  mutiply(String number1,String number2){
		int len1=number1.length();
		int len2=number2.length();
		final int []number=new int[len1+len2];//定义一个长度为两个数字长度之和的数组用来存储计算结果
		int max=len1>len2?len1:len2;
		int min=max==len1?len2:len1;
		String maxStr=len1>len2?number1:number2;
		String minStr=maxStr==number2?number1:number2;
		int carryFlag=0;//进位标记
		int cusor=number.length-1;//数组移动游标
		int index=0;
		char []bigChar=maxStr.toCharArray();
		char []smallChar=minStr.toCharArray();
		for(int i=min-1;i>=0;i--){
			int big=new Integer(smallChar[i]+"");
			index=cusor;
			carryFlag=0;
			for(int j=max-1;j>=0;j--){
				int small=new Integer(bigChar[j]+"");;
				int result=(big*small+number[index]+carryFlag);
				carryFlag=result/10;
				number[index]=result%10;
			index--;
			}
			cusor--;
			 number[index]=carryFlag;
		}
	
	  
		
		return toString(number);
	}
	/**
	 * 两个大整数相加
	 * @param number1
	 * @param number2
	 * @return
	 */
	
	public static String Add(String number1,String number2){
		int len1=number1.length();
		int len2=number2.length();
		int max=len1>len2?len1:len2;
		int min=max==len1?len2:len1;
		String maxStr=len1>len2?number1:number2;
		final int []number=new int[max+1];//定义一个长度为两个数字长度之和的数组用来存储计算结果
		String minStr=maxStr==number2?number1:number2;
		int carryFlag=0;//进位标记
		int cusor=number.length-1;//数组移动游标
		char []bigChar=maxStr.toCharArray();
		char []smallChar=minStr.toCharArray();
		int index=min-1;
			for(int j=max-1;j>=0;j--){
				int big=new Integer(bigChar[j]+"");
			 if(index>=0){
				 int small=new Integer(smallChar[index]+"");
				 int result=(big+small+number[cusor]+carryFlag);
					carryFlag=result/10;
					number[cusor]=result%10;
					 index--;
				
			 }
			 else{
				 int result=(big+carryFlag);
				 carryFlag=result/10;
					number[cusor]=result%10;
			 }
			 cusor--;
			}
			
	
		return toString(number);
	}
	
	/**
	 * 两个大整数相减
	 * @param number1
	 * @param number2
	 * @return
	 */
	public static String reduce(String number1,String number2){
		int len1=number1.length();
		int len2=number2.length();
		int max=len1>len2?len1:len2;
		int min=max==len1?len2:len1;
		String maxStr=len1>len2?number1:number2;
		final int []number=new int[max];//定义一个长度为两个数字长度之和的数组用来存储计算结果
		String minStr=maxStr==number2?number1:number2;
		int borrowFlag=0;//借位标记
		int cusor=number.length-1;//数组移动游标
		char []bigChar=maxStr.toCharArray();
		char []smallChar=minStr.toCharArray();
		int index=min-1;
			for(int j=max-1;j>=0;j--){
				int big=new Integer(bigChar[j]+"")-borrowFlag;
			 if(index>=0){
				 int small=new Integer(smallChar[index]+"");
				 int result=(big-small)<0?big+10-small:big-small;
				 borrowFlag=(big-small)<0?1:0;
					 index--;
					 number[cusor]=result;
				
			 }
			 else{
				 int result=(big-borrowFlag)<0?big+10-borrowFlag:big-borrowFlag;
				 borrowFlag=(big-borrowFlag)<0?1:0;
				 number[cusor]=result;
			 }
			 cusor--;
			}
			
	
		return toString(number);
	
	}
	
	public static String toString(int []number){
		StringBuilder numBulider=new StringBuilder(number.length);
		for(int len=number.length,i=0;i<len;i++){
			if(number[i]==0&&i==0){
				continue;
			}
			numBulider.append(number[i]);
		}
		return numBulider.toString();
	}
	/**
	 * 判断是否是回文
	 * @param str
	 * @return
	 */
	public static boolean isHuiWen(String s){
		for(int i=0,len=s.length(),j=len-1;i<len/2;i++,j--){
			char head=s.charAt(i);
			char bottom=s.charAt(j);
			if(head!=bottom){
				return false;
			}
		}
		return true;
	}
	
	private static String maxStr="";//最长字符标记串
	private static String longest="";
	/**
	 * 递归遍历最长回文串
	 * @param in
	 * @param start
	 * @param end
	 * @param length
	 */
	static void printAllChar(String in, int start, int end,int length){
		if(end>=start)
		 maxStr=in.substring(start,end);
		
		boolean ishui=isHuiWen(maxStr.trim());
		if(ishui){
		if(maxStr.length()>1
				&&maxStr.length()>=longest.length()){
				longest=maxStr;
		
			
		}
		}

		if(end>=1){
			
			printAllChar(in,start,end-1,length);
			
			

		} 
		if(end==1&&start<length-1){
			printAllChar(in,start+1 , length, length);
		}
	
		


	}
	/**
	 * 取得最长回文串
	 * @return
	 */
	public static String getMaxString(){
		return longest.toString();
	}
	
	public static void main(String[] args) {
		System.out.println(reduce("1111", "1699"));
	
		String s="";
	//String huiwen="1123xxxxxxxxxxxxxxxxxxxxxx3211bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb3211";
	
	System.out.println(s.length());
	System.out.println(mutiply("11111111999999999999999999999991111111199999999999111111119999999999999999999999911111111999999999999999999111111119999999999999999999999911111111999999999991111111199999999999999999999999111111119999999999999999999999999999999999999991111111199999999999999999999999111111119999999999911111111999999999999999999999991111111199999999999999999999999999999999999999911111111999999999999999999999991111111199999999999111111119999999999999999999999911111111999999999999999999999999999999999999999999999999999999999999", "1111111199999999999999999999999111111119999999999911111111999999999999999999999991111111199999999999999999999999999999999999999911111111999999999999999999999991111111199999999999111111119999999999999999999999911111111999999999999999999999999999999999999999"));
	System.out.println(new BigDecimal("11111111999999999999999999999991111111199999999999111111119999999999999999999999911111111999999999999999999999999999999999999999").multiply(new BigDecimal("999999999999999999999999")).doubleValue());
	}

}