总和等于X的数组值 [英] Sum array values with sum equals X

问题描述

我有一个整数集合.我需要获得所有值总和等于X的可能性.

I have an integer collection. I need to get all possibilites that sum of values are equal to X.

我需要类似此的东西.

它可以用以下语言编写:delphi，c#，php，RoR，python，cobol，vb，vb.net

It can be written in: delp c#, php, RoR, python, cobol, vb, vb.net

推荐答案

这是子集总和问题.它是 NP完全.

实现此目的的唯一方法是生成所有可能的组合并比较总和值.不过存在优化技术.

The only way to implement this would be generate all possible combinations and compare the sum values. Optimization techniques exists though.

这是C#中的一个:

static class Program
{
    static int TargetSum = 10;
    static int[] InputData = new[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

    static void Main()
    {
        // find all permutations
        var permutations = Permute(InputData);

        // check each permutation for the sum
        foreach (var item in permutations) {

            if (item.Sum() == TargetSum) {

                Console.Write(string.Join(" + ", item.Select(n => n.ToString()).ToArray()));
                Console.Write(" = " + TargetSum.ToString());
                Console.WriteLine();

            }
        }

        Console.ReadKey();
    }

    static IEnumerable<int[]> Permute(int[] data) { return Permute(data, 0); }

    static IEnumerable<int[]> Permute(int[] data, int level)
    {
        // reached the edge yet? backtrack one step if so.
        if (level >= data.Length) yield break;

        // yield the first #level elements
        yield return data.Take(level + 1).ToArray();

        // permute the remaining elements
        for (int i = level + 1; i < data.Length; i++) {
            var temp = data[level];
            data[level] = data[i];
            data[i] = temp;

            foreach (var item in Permute(data, level + 1))
                yield return item;

            temp = data[i];
            data[i] = data[level];
            data[level] = temp;
        }

    }
}

这篇关于总和等于X的数组值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！