使用加权概率和值在数组中查找项目 [英] Find item in array using weighed probability and a value

问题描述

上周我遇到了一些我正在做的简单程序的问题，而且有人帮我了。现在我遇到了另一个问题。
我目前有这个代码：

Last week I had some problems with a simple program I am doing and somebody here helped me. Now I have run into another problem. I currently have this code:

var findItem = function(desiredItem) {
    var items = [
        { item: "rusty nail", probability: 0.25 },
        { item: "stone", probability: 0.23 },
        { item: "banana", probability: 0.20 },
        { item: "leaf", probability: 0.17 },
        { item: "mushroom", probability: 0.10 },
        { item: "diamond", probability: 0.05 }
    ];
    var possible = items.some( ({item, probability}) => 
          item === desiredItem && probability > 0 );
    if (!possible) {
        console.log('There is no chance you\'ll ever find a ' + desiredItem);
        return;
    }
    var sum = items.reduce( (sum, {item, probability}) => sum+probability, 0 );
    while (true) {
        var value = Math.random() * sum;
        var lootedItem = items.find( 
                ({item, probability}) => (value -= probability) <= 0 ).item;
        if (lootedItem === 'diamond') break;
        console.log("Dang! A " + lootedItem + " was found...");
    }
    console.log("Lucky! A " + desiredItem + " was found!");
}

findItem('diamond');

现在我想通过在中添加另一个名为 category 的值来扩展它items 数组。我希望类别的值为 2 ， 5 或 10 。因此，假设钻石项目属于类别：10 ，以及 findItem ，只能找到属于同一类别的项目。我已经尝试了几天，但似乎无法理解它。也许有人可以帮我推动正确的方向？提前致谢

Now I would like to expand on this by adding another value called category to the items array. I want the categories to have a value of either 2, 5 or 10. So let's say the diamond item would belong to category: 10, and when findItem is executed only items that belong to the same category can be found. I have been trying for a couple of days now but can't seem to get my head around it. Maybe someone can help push me in the right direction? Thanks in advance

推荐答案

您可以将此更新用于该代码：

You could use this update to that code:

// Pass the item list and the desired category as arguments:
var findItem = function(items, category, desiredItem) {
    // apply filter to items, so only those of the given category remain:
    items = items.filter( item => item.category == category );
    // rest of code remains the same:
    var possible = items.some( ({item, probability}) => 
          item === desiredItem && probability > 0 );
    if (!possible) {
        console.log('There is no chance you\'ll ever find a ' + desiredItem);
        return;
    }
    var sum = items.reduce( (sum, {item, probability}) => sum+probability, 0 );
    var t = 10;
    while (true) {
        var value = Math.random() * sum;
        var lootedItem = items.find( 
                ({item, probability}) => (value -= probability) <= 0 ).item;
        if (lootedItem === desiredItem) break; // fixed this condition!
        console.log("Dang! A " + lootedItem + " was found...");
        t--; if (t <= 0) throw "loop";
    }
    console.log("Lucky! A " + desiredItem + " was found!");
}

// Define items here with their category
var items = [
    { item: "rusty nail", probability: 0.25, category:  2 },
    { item: "stone",      probability: 0.23, category:  2 },
    { item: "banana",     probability: 0.20, category:  2 },
    { item: "leaf",       probability: 0.17, category:  5 },
    { item: "mushroom",   probability: 0.10, category:  5 },
    { item: "diamond",    probability: 0.05, category: 10 }
];

// Call function with extra arguments:
findItem(items, 5, 'mushroom');

console.log('second run:');
// This will obviously give a hit immediately, as there is only one possible item:
findItem(items, 10, 'diamond');

更改为：

• 将更多参数传递给您的函数：项目列表和所需类别


• 在项目列表中应用过滤器作为函数中的第一个操作


• 修复了与 lootedIt有关的问题em test - 它有菱形硬编码。


• 定义函数外部的项目列表，并为每个元素添加类别值。


• 调整函数的调用以传递额外的参数。

• Pass more arguments to your function: the items list and the desired category
• Apply a filter on the items list as first action in the function
• Fix an issue concerning the lootedItem test -- it had "diamond" hard-coded.
• Define the items list outside of the function and add category values to each element.
• Adapt the call of the function to pass the extra arguments.

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