C++程序设计的算法解决问题

Question

1，问题描述：在下面的算式中，添加“+”、“-”，“*”，“/”,4个运算符，使得这个式子成立。
5 5 5 5 5=5，不用枚举算法解决，用别的算法解决，求代码

Answer 1

递归解决

using System;
using System.Linq;
using System.Collections.Generic;
using System.Text.RegularExpressions;

namespace Q760027
{
    class Program
    {
        static IEnumerable<string> solve(string s, int[] v, int t)
        {
            if (v.Length == 2)
            {
                if (v[0] + v[1] == t) yield return s + "+";
                if (v[0] - v[1] == t) yield return s + "-";
                if (v[0] * v[1] == t) yield return s + "*";
                if (v[1] != 0 && v[0] % v[1] == 0) { if (v[0] / v[1] == t) yield return s + "/"; }
                yield break;
            }
            foreach (var item in solve(s + "+", new int[] { v[0] + v[1] }.Concat(v.Skip(2)).ToArray(), t))
                yield return item;
            foreach (var item in solve(s + "-", new int[] { v[0] - v[1] }.Concat(v.Skip(2)).ToArray(), t))
                yield return item;
            foreach (var item in solve(s + "*", new int[] { v[0] * v[1] }.Concat(v.Skip(2)).ToArray(), t))
                yield return item;
            if (v[1] != 0 && v[0] % v[1] == 0)
            {
                foreach (var item in solve(s + "/", new int[] { v[0] / v[1] }.Concat(v.Skip(2)).ToArray(), t))
                    yield return item;
            }
        }

        static void Main(string[] args)
        {
            foreach (string s in solve("", new int[] { 5, 5, 5, 5, 5 }, 5).Where(x => !Regex.IsMatch(x, @"[\+\-][\*\/]")))
                Console.WriteLine(s);
        }
    }
}

++--
+-+-
+--+
-++-
-+-+
--++
**//
*/+-
*/-+
*/*/
*//*
/*+-
/*-+
/**/
/*/*

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