JavaScript-given a value, such as 100, given an array, select n elements from the array, and the n elements add up to 100, to get a result.

Array:

var arr = [99.1, 92.2, 60, 50,           49.5, 45.7, 25.1, 20,            17.4, 13, 10, 7, 2.1, 2, 1];

The array elements that are found and are 100:

[60,20,10,7,2,1]

Reply content:

Array:

var arr = [99.1, 92.2, 60, 50,           49.5, 45.7, 25.1, 20,            17.4, 13, 10, 7, 2.1, 2, 1];

The array elements that are found and are 100:

[60,20,10,7,2,1]

function f($n, $arr) { //$n是目标数字，$arr是数字组成的数组    if (empty($arr)) return false; //如果数组没有元素，返回    if (in_array($n, $arr)) return [$n];//如果期望的值已经存在，直接返回这个值    foreach($arr as $k => $v) { //遍历数组        if ($v > $n) continue; //比指定数还大，过        $copy = $arr; //复制数组        unset($copy[$k]); //去掉复制数组中已经被选中的数字        $next = f($n - $v, $copy); //递归计算        if(! empty($next)) return array_merge([$v], $next); //合并结果集    }    

To the Python version:

def subsetsum(elements, target):    if target==0:        return True, []    elif not elements or target < 0:        return False, None    result, subset = subsetsum(elements[:-1], target-elements[-1])    return (True, subset + [elements[-1]]) if result else subsetsum(elements[:-1], target)

The idea is simple, and when I ask elements if it can be added target , there are only two possibilities:

1. I'm going to use it to add-- element[-1] target I'm going to be able to use elements[:-1] the add-out target-elements[-1] .

2. I don't need to use element[-1] it to add-I'm target going to be able to use elements[:-1] the add-out target .

Boundary condition is:

1. target 0 That's when I'm not going to be able to add anything on my behalf, soreturn True, []

2. When it elements 's empty or target negative, the rep never comes out, soreturn False, None

Tests :

elements = [99.1, 92.2, 60, 50, 49.5, 45.7, 25.1, 20, 17.4, 13, 10, 7, 2.1, 2, 1]target = 100result, subset = subsetsum(elements, target)print(result, subset)

Results :

True [60, 20, 10, 7, 2, 1]

The problem is that it is more interesting to see the problem, if you have to think about the speed of the solution, and so on.

Having done this research, I present a variation of the problem that you can consider to look at:

We are going to set an integer (which represents the negative) for the Multiset (Multiset is a set, but allow elements to be repeated), called, in order to set elements another integral multi-set called targets , to ask whether there are several sub-sets, the elements of each child multiset and exactly one in the .

The definition does not understand is not bad, I take an example:

elements = (1,4,6,4,1)targets = (5,10,1)

There are solutions to this example:

(1,4) -> 5(4,6) -> 10(1) -> 1

Note that each element in the in elements can only be used once!

Combinatorial issues. Take a look at Leetcode's original question:

function t100(array){  var tempArray = array.concat([]).sort(function(a,b){    return a-b;  });  var temp = 0;  var result = [];  for(var i=0;i
  
   
    
   100){      tempArray.length = i;    }  }  for(var i=0;i
   
    < code="">
   
  

递归内套一个循环

