还不能处理负数和小数点
package s1;
import java.util.Stack;
import java.util.Vector;
/** *//**
* A multiply simulation
* for example :
* 56 X 67 =
*
* 56
* x 67
* ----------
* 392
* 336
*------------
* 3752
*
* So ,in this way,We can calculation very very big number,for example: 299^133 etc.
*
* @author Urashima
*
*/
public class BigNumberMultiply extends BaseNumberOperation
{
//each array indicates a param
private Integer[] paramFirst,paramSecond;
//main method
public String calculate(String param1,String param2){
paramFirst = convert(param1);
paramSecond = convert(param2);
//multiply each bit,from low to high
int indexFirst = paramFirst.length - 1;
int indexSecond = paramSecond.length - 1;
//multiply results for each bit
Vector<Integer[]> branchResults = new Vector<Integer[]>();
for(;indexSecond > -1;indexSecond--){
branchResults.add(branchMultiply(paramFirst,paramSecond[indexSecond]));
}
String finalResult = branchAddTogether(branchResults);
return finalResult;
}
private Integer[] branchMultiply(Integer[] upper,Integer down){
Stack<Integer> results = new Stack<Integer>();
//todo : all core gose here
int carryFlag = 0;
for(int index = upper.length-1 ;index > -1;index--){
int r1 = down;
int r2 = upper[index];
int r0 = r1 * r2 + carryFlag;
carryFlag = (int)(r0/10);
int r3 = r0 - ( 10 * carryFlag );
if(index!=0)
results.push(r3);
else
results.push(r0);
}
//sorts out and return
Integer[] branchResult = new Integer[results.size()];
results.toArray(branchResult);
//System.out.println (branchResult.toString());
return branchResult;
}
private String branchAddTogether(Vector<Integer[]> v){
Vector<String> params = new Vector<String>();
//TODO: fix bug#001
int bi = 0;
for(Integer[] pps : v){
//revers pps
Integer[] rpps = new Integer[pps.length];
System.arraycopy(pps,0,rpps,0,pps.length);
for(int k = pps.length-1 ; k > -1 ; k-- ){
rpps[pps.length-1-k] = pps[k];
}
v.set(bi++,rpps);
}
//sort out data,add increamental 0 to each bit
for(Integer[] ii : v){
String pa = "";
for(Integer i : ii){
pa += i;
}
params.add(pa);
}
int incr = 0;
for(int idx = 0 ; idx < params.size(); idx ++){
String s = params.get(idx);
for(int i = 0 ; i < incr ; i ++){
s += "0";
}
params.set(idx,s);
//System.out.println (s);
incr++;
}
//convert back to int[]
for(int i = 0 ; i < params.size();i++){
String ctt = params.get(i);
//System.out.println (ctt);
v.set(i,convert(ctt));
}
//add them together
Stack<Integer> result;
//trim right and add
result = trimRightAdd(v);
StringBuffer sb = new StringBuffer();
try{
while(true)
sb.append(result.pop());
}catch(Exception e){
//pass,ignore.
}
return sb.toString();
}
private Stack<Integer> trimRightAdd(Vector<Integer[]> params){
Stack<Integer> result = new Stack<Integer>();
int carry = 0;
int maxBit = 0;
//todo:maxbit
for(Integer[] i : params){
int il = i.length;
maxBit = il > maxBit?il:maxBit;
}
//bit moving , from low to higth
int indexDecreaseCount = 1;
int columnValue = 0;
int bitValue = 0;
for(int k = 0 ; k < maxBit; k++){
if(k > 0){
result.push(bitValue);
columnValue = 0;
bitValue = 0;
}
//value of each column,including carry
int num = 0;
for(Integer[] param : params){
int index = param.length - indexDecreaseCount;
try{
num = param[index];
}catch(Exception e){
num = 0;
}
//TODO: may be simulation calculate is better here
columnValue += num;
}
//first bit
if(k != maxBit-1 ){
columnValue += carry;
carry = (int)(columnValue/10);
bitValue = columnValue - ( 10 * carry );
indexDecreaseCount ++;
}else{
columnValue += carry;
result.push(columnValue);
}
}
return result;
}
}测试计算结果
package s1;
public class Demo{
private TwoNumberOperation operatorMultiply = new BigNumberMultiply();
public void multiplyDemo(String param1,String param2){
String result = operatorMultiply.calculate(param1,param2);
System.out.println (param1+" x "+param2+" = "+result);
}
public static void main (String[] args) {
Demo demo = new Demo();
demo.multiplyDemo("12","12");
demo.multiplyDemo("56","67");
demo.multiplyDemo("3459398","11667278");
demo.multiplyDemo("9283736253829832323432342342543654576343534564353734534534534534534553773453453453453453455377345345345345345345537734534534534534534553773453453453453453455377345345345345345345537734534534534534534553745645545",
"23470926947345345345345345345537734534534534534534553773453453453453453455377345345345345345345537734534534534534534553773453453453453453455377345345345345345345537734534534534534534553773453453453453453455377345345345345345345537863053758734076407083760987207345345345345345345537693709479");
}
}
--------------------Configuration: <Default>--------------------
12 x 12 = 144
56 x 67 = 3752
3459398 x 11667278 = 40361758178644
9283736253829832323432342342543654576343534564353734534534534534534553773453453453453453455377345345345345345345537734534534534534534553773453453453453453455377345345345345345345537734534534534534534553745645545 x 23470926947345345345345345345537734534534534534534553773453453453453453455377345345345345345345537734534534534534534553773453453453453453455377345345345345345345537734534534534534534553773453453453453453455377345345345345345345537863053758734076407083760987207345345345345345345537693709479 = 217897895412061538535213749538424917178427642790309526149197050342787946552594940694811082625513148107368458788645637103672066743646902872289253339664141494118086813947265391829794894470256056436951017797373234350763998817946444452982381515332165838866556971112151531240855136817304521889160157930869290050844235614446072972714978233006835557537630008993034139267140464023218920328137852716504553853724234899138660678581541565601300563516326950021051186577024411324340905167953542819936071934540621055
Process completed.