如何解决如何从加权列表中选择4个唯一项？
| 因此，我有一个加权项目列表，我想从该列表中选择4个非重复项目。Item Weight
Apple 5
Banana 7
Cherry 12
...
Orange 8
Pineapple 50
解决方法
在您的评论中，您说独特是指：
我不想选择相同的项目两次。
..权重决定了被拣选的可能性。
要确保您没有选择重复项，只需要做的就是在选择下一个项目之前先从列表中删除最后一个项目。是的，这将稍微改变您的体重，但是如果您确实希望获得独特的结果，那么这是正确的统计更改。
此外，我不确定您是如何使用权重来确定候选者的，但是我想出了该算法，该算法应使用最少的循环次数（并且无需根据权重填充数组，可能会导致数组过大，需要int权重等）。
我在这里使用过JavaScript，只是为了轻松在没有服务器的浏览器中查看输出。移植到PHP应该很简单，因为它没有做任何复杂的事情。
常数
var FRUITS = [
{name : \"Apple\",weight: 8 },{name : \"Orange\",weight: 4 },{name : \"Banana\",{name : \"Nectarine\",weight: 3 },{name : \"Kiwi\",weight: 1 }
];
var PICKS = 3;
function getNewFruitsAvailable(fruits,removeFruit) {
var newFruits = [];
for (var idx in fruits) {
if (fruits[idx].name != removeFruit) {
newFruits.push(fruits[idx]);
}
}
return newFruits;
}
var results = [];
var candidateFruits = FRUITS;
for (var i=0; i < PICKS; i++) {
// CALCULATE TOTAL WEIGHT OF AVAILABLE FRUITS
var totalweight = 0;
for (var idx in candidateFruits) {
totalweight += candidateFruits[idx].weight;
}
console.log(\"Total weight: \" + totalweight);
var rand = Math.random();
console.log(\"Random: \" + rand);
// ITERATE THROUGH FRUITS AND PICK THE ONE THAT MATCHES THE RANDOM
var weightinc = 0;
for (idx in candidateFruits) {
// INCREMENT THE WEIGHT BY THE NEXT FRUIT\'S WEIGHT
var candidate = candidateFruits[idx];
weightinc += candidate.weight;
// IF rand IS BETWEEN LAST WEIGHT AND NEXT WEIGHT,PICK THIS FRUIT
if (rand < weightinc/totalweight) {
results.push(candidate.name);
console.log(\"Pick: \" + candidate.name);
// GET NEXT SET OF FRUITS (REMOVING PICKED FRUIT)
candidateFruits = getNewFruitsAvailable(candidateFruits,candidate.name);
break;
}
}
console.log(\"CandidateFruits: \" + candidateFruits.length);
};
for (var i=0; i < results.length; i++) {
document.write(results[i] + \"<br/>\");
}
[0,1)
function array_rand2($ary,$n = 1)
{
// make sure we don\'t get in to an infinite loop
// check we have enough options to select from
$unique = count(array_unique(array_keys($ary)));
if ($n > $unique) $n = count($unique);
// First,explode the array and expand out all the weights
// this means something with a weight of 5 will appear in
// in the array 5 times
$_ary = array();
foreach ($ary as $item => $weight)
{
$_ary = array_merge($_ary,array_fill(0,$weight,$item));
}
// now look for $n unique entries
$matches = array();
while (count($matches) < $n)
{
$r = $_ary[array_rand($_ary)];
if (!in_array($r,$matches))
{
$matches[] = $r;
}
}
// and now grab those $n entries and return them
$result = array();
foreach ($matches as $match){
$result[] = $match;
}
return $result;
}
list.elementAt(rand_index++ % size(list))
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