import java.util.Scanner; public class Main { private static int n,m,k; private static int[] aa,numm,fig; private static boolean[] used; public static void main(String[] args){ Scanner input = new Scanner(System.in); while (true){ n = input.nextInt(); m = input.nextInt(); aa = new int[n]; numm = new int[n]; fig = new int[n]; used = new boolean[n]; for(int i=0; i<n; i++){ aa[i] = input.nextInt(); used[i] = false; } for(k=0; k<n; k++){ if(search(0)){ System.out.println(k); out(); return; } } System.out.println("No Solution!"); } } private static boolean search(int dep){ if(dep > k){ return found(); } for(int i=0; i<n; i++) if(!used[i]){ numm[dep] = aa[i]; used[i] = true; for(int j=0; j<4; j++){ fig[dep] = j; if(search(dep+1)) return true; } used[i] = false; } return false; } private static boolean found(){ int x = numm[0]; for(int i=0; i<k; i++){ switch (fig[i]) { case 0 -> x += numm[i + 1]; case 1 -> x -= numm[i + 1]; case 2 -> x = numm[i + 1]; case 3 -> x /= numm[i + 1]; } } return (x==m); } private static void out(){ System.out.print(numm[0]); for(int i=0; i<k; i++) switch (fig[i]) { case 0 -> { System.out.print("+" + numm[i + 1]); continue; } case 1 -> { System.out.print("-" + numm[i + 1]); continue; } case 2 -> { System.out.print("" + numm[i + 1]); continue; } case 3 -> { System.out.print("/" + numm[i + 1]); continue; } } } } 修改为c++实现

下面是将Java代码转换为C++代码的实现：

#include<bits/stdc++.h>
using namespace std;

int n,m,k;
int aa[100],numm[100],fig[100];
bool used[100];

bool search(int dep);
bool found();
void out();

int main()
{
    while (scanf("%d%d",&n,&m)==2)
    {
        for(int i=0;i<n;i++)
        {
            scanf("%d",&aa[i]);
            used[i]=false;
        }
        for(k=0;k<n;k++)
        {
            if(search(0))
            {
                printf("%d\n",k);
                out();
                printf("\n");
                break;
            }
        }
        if(k==n)
            printf("No Solution!\n");
    }

    return 0;
}

bool search(int dep)
{
    if(dep>k)
        return found();
    for(int i=0;i<n;i++)
    {
        if(!used[i])
        {
            numm[dep]=aa[i];
            used[i]=true;
            for(int j=0;j<4;j++)
            {
                fig[dep]=j;
                if(search(dep+1))
                    return true;
            }
            used[i]=false;
        }
    }
    return false;
}

bool found()
{
    int x=numm[0];
    for(int i=0;i<k;i++)
    {
        switch(fig[i])
        {
            case 0:x+=numm[i+1];break;
            case 1:x-=numm[i+1];break;
            case 2:x=numm[i+1];break;
            case 3:x/=numm[i+1];break;
        }
    }
    return (x==m);
}

void out()
{
    printf("%d",numm[0]);
    for(int i=0;i<k;i++)
    {
        switch(fig[i])
        {
            case 0:printf("+%d",numm[i+1]);break;
            case 1:printf("-%d",numm[i+1]);break;
            case 2:printf("%d",numm[i+1]);break;
            case 3:printf("/%d",numm[i+1]);break;
        }
    }
}