第十二届蓝桥杯F题

递归。

#include<iostream>
# include <cstdio>
# include <vector>
# include <algorithm>
# define ll long long
using namespace std;
int a[101];int n;
int b[3]={-1,0,1};
int w[100001];
void fx(int i,int weight)
{
    if(i==n+1)
    {
        if(weight>=1&&weight<=100000)
        {
            ++w[weight];
        }
    }
    else
    {
        for(int j=0;j<3;++j)
        {
            fx(i+1,weight+a[i]*b[j]);
        }
    }
}
int main(){
    cin>>n;
    int i;
    for(i=1;i<=n;++i)
    {
        cin>>a[i];
    }
    fx(1,0);int sum=0;
    for(i=1;i<=100000;++i)
    {
        if(w[i])
            ++sum;
    }
    cout<<sum<<endl;
    return 0;
}