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A Simple Tool Operations Class
package com.luues.util.number;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class Sum {
/**
* 快速找出keys里面的数字相加的和等于kill的值的组合方式
* @param keys 数值数组
* @param kill 和
* @return
*/
public static List getNum(List keys, double kill) {
int n = keys.size();
int nbit = 1 << n;
double in;
List list = new ArrayList();
for (int i = 0; i < nbit; i++) {
in = 0;
list.clear();
for (int j = 0; j < n; j++) {
int tmp = 1 << j; // 由0到n右移位
if ((tmp & i) != 0) { // 与运算，同为1时才会是1
in += keys.get(j);
list.add(keys.get(j));
}
}
if (in == kill)
return list;
}
return list;
}
public static List> getNums(List> keys, double kill) {
int n = keys.size();
int nbit = 1 << n;
double in;
List> list = new ArrayList>();
for (int i = 0; i < nbit; i++) {
in = 0;
list.clear();
for (int j = 0; j < n; j++) {
int tmp = 1 << j; // 由0到n右移位
if ((tmp & i) != 0) { // 与运算，同为1时才会是1
Map map = keys.get(j);
for(Integer key : map.keySet()){
in += map.get(key);
}
list.add(keys.get(j));
}
}
if (in == kill)
return list;
}
return new ArrayList>();
}
}