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javascript - 如何比较决策树的单个路径？

问题描述

我想在 javascript 的一个函数中比较决策树的单个路径。

我只知道如何做到这一点，因为节点正在加起来，但那只是比较节点。相反，我想查看一条路径，然后查看下一条路径。

例如：下一个决定应该是range-3。给出的是数字[9, 8, 6, 5, 3, 2, 0]。列表的总和是value。length需要6的路径biggest value。

                      2 - 0
                  3 <
               5<     0 
             /    2 - 0
           6 
          /  \    2 - 0
               3<
                  0
     8         2 - 0
       \    3<
   /    5 <    0
            2 - 0

9               2 - 0
            3 <
         5<     0 
   \   /    2 - 0
     6 
       \   2 - 0
        3<
           0

我想比较那些paths：

[9,6,3,0],
[9,6,3,2,0],
[9,6,5,2,0],
[9,6,5,3,0],
[9,6,5,3,2,0],
[9,8,6,3,0],
[9,8,6,3,2,0],
[9,8,6,5,2,0],
[9,8,6,5,3,0],
[9,8,6,5,3,2,0],

而不是计算每个path然后同时比较它们，我只想计算第一个path，然后将它与第二个进行比较，path如下所示：

[9,6,3,0], //value 18
[9,6,3,2,0]//value 21

   || which one has the nearest length of 6 with the most Value?
   \/
[9,6,3,2,0]//value 21

[9,6,3,2,0],//value 21
[9,6,5,2,0] //value 23

   || which one has the nearest length of 6 with the most Value?
   \/ 
[9,6,5,2,0] //value 23

... and so on

如何一次只比较 2 条路径而不是每条路径？

编辑1：

到目前为止我的代码： https ://replit.com/@RubyKanima/BestSumwithlength#index.js

const numbers = [9, 8, 6, 5, 3, 2, 0];
const starting_node = Math.max(...numbers) + 3;

const path = (current_node, memo ={}) => {
  if (current_node in memo) return memo[current_node];
  if (current_node == 0) return [[]];
  let paths = [];
  let tmp_nodes = [];
  for (n of numbers) {
    if (n >= current_node - 3 && n < current_node) {
      tmp_nodes.push(n);
    }
  }
  for (let tmp of tmp_nodes) {
    const tmp_path = path(tmp);
    const tmp_paths = tmp_path.map(way => [tmp, ...way]);
    paths.push(...tmp_paths);
  }
  memo[current_node] = paths; 
  paths = paths.filter(x => x.length <= 6);
  return paths;
};

const bestPath = all_paths => {
  all_paths = all_paths.filter(x => (x.length = 6));
  let bestValue = 0;
  let bestPath = null;
  for (let path of all_paths) {
    let value = 0;
    for (node of path) value += node;
    if (value > bestValue) {
      bestValue = value;
      bestPath = path;
    }
  }
  return bestPath;
};
const path_array = path(starting_node);
console.log(bestPath(path_array));

它完成了这项工作，但如果我得到超过一千个数字，它就会出现堆栈溢出。（在示例中，我减少了一些数字以便于理解，实际上范围是 -360 而不是 -3）

最大的问题：数据太多

如何解决？：一次只比较 2 条路径，然后计算下一条路径。

我想知道的：如何只计算 2 条路径。

标签： javascriptarraysdynamic

解决方案

因此，我编写了一个合并排序算法，并为您的解决方案和合并排序解决方案添加了一些性能时间计算。在这种情况下，合并排序似乎表现更好。它同时比较两个数组，直到达到您需要的数组。在你的数据上试试这个，它应该更大，看看它是否效果更好。

const numbers = [9, 8, 6, 5, 3, 2, 0];
const starting_node = Math.max(...numbers) + 3;

const path = (current_node, memo ={}) => {
  if (current_node in memo) return memo[current_node];
  if (current_node == 0) return [[]];
  let paths = [];
  let tmp_nodes = [];
  for (n of numbers) {
    if (n >= current_node - 3 && n < current_node) {
      tmp_nodes.push(n);
    }
  }
  for (let tmp of tmp_nodes) {
    const tmp_path = path(tmp);
    const tmp_paths = tmp_path.map(way => [tmp, ...way]);
    paths.push(...tmp_paths);
  }
  memo[current_node] = paths; 
  paths = paths.filter(x => x.length <= 6);
  return paths;
};

const bestPath = all_paths => {
  all_paths = all_paths.filter(x => (x.length = 6));
  let bestValue = 0;
  let bestPath = null;
  for (let path of all_paths) {
    let value = 0;
    for (node of path) value += node;
    if (value > bestValue) {
      bestValue = value;
      bestPath = path;
    }
  }
  return bestPath;
};
//-----merge sort algorithm---------
const sumArr = arr => arr.reduce((acc, next)=> acc+next)
function merge(arr1, arr2){
    if (sumArr(arr1) > sumArr(arr2)) {
        return arr1
    } else if(sumArr(arr1) < sumArr(arr2)) {
        return arr2
    } else {return arr1}
}
function mergeSort(arr){
    if(arr.length <= 1) return arr[0];
    let mid = Math.floor(arr.length/2);
    let left = mergeSort(arr.slice(0,mid));
    let right = mergeSort(arr.slice(mid));
    return merge(left, right);
}
//-----end of merge sort algorithm------

const path_array = path(starting_node);
const start = performance.now()
console.log(bestPath(path_array));
const end = performance.now()
console.log("bestPath performance ", end-start)
const start2 = performance.now()
console.log(mergeSort(path_array))
const end2 = performance.now()
console.log("mergeSort performance ", end2-start2)

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