组合总数计算

package test;

import java.util.HashMap;
import java.util.Map;

/**
 * @author QuarterLifeForJava
 * 极其简单初级的实现
*/
public class Test {
	public static void main(String[] args) {
		int arry[] = {1,2,3,4,5,6};
		int count = conditionTimes(arry);
		int rest = arry.length - count;
		if(rest == 0){//A(n)(n)种组合
			int result = resultCount(arry.length,arry.length);
			System.out.println(result);
		}else{//A(n)(n-重复数字+1)除以A(重复数字)(1)
			int result = resultCount(count,arry.length)/resultCount(1,(rest+1));
			System.out.println(result);
		}
	}
	
	public static int conditionTimes(int arry[]){
		Map<Integer,Integer> map = new HashMap<Integer, Integer>();
		for(int i=0;i<arry.length;i++){
			map.put(arry[i], arry[i]);
		}
		return map.size();
	}
	
	public static int resultCount(int start,int end){
		int result = 1;
		for(int i=1;i<=start;i++){
			result*=end;
			end--;
		}
		return result;
	}
	
}