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简单dfs

题目要求非常扯淡 按优先输出不包含n的, 其次n-1的

所以dfs时记录路径, 按要求cmp sort

时间31ms

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 7; 
typedef long long ll;

ll n, sum;
ll arr[MAXN] = {0};

struct node
{
	int brr[30], len;
}ans[MAXN];

ll pos = 0;

bool cmp(node a, node b)
{
	ll x = 0, y = 0;

    for(int i = 0; i <= a.len; i++)
    {
        x = x + (1 << a.brr[i]);
    }

    for(int j = 0; j <= b.len; j++)
    {
        y = y + (1 << b.brr[j]);
    }

    return x < y;
}

void dfs(ll now, ll rsum, ll step)
{
	if(step > n)
		return ; 
	ans[pos].brr[step] = now;
	
	if(sum == rsum)
	{
		ans[pos].len = step;
		++pos;
		
		for(int i = 0; i <= step; i++)
			ans[pos].brr[i] = ans[pos - 1].brr[i];
	}
	
	for(int i = now + 1; i < n; i++)
	{
		dfs(i, rsum + arr[i], step + 1);
	}
}

int main()
{
	
	cin>>n;
	
	for(int i = 0; i < n; i++)
		cin>>arr[i];
	
	cin>>sum;
	
	for(int i = 0; i < n; i++)
	{
		dfs(i, arr[i], 0);	
	}
	
	sort(ans, ans + pos, cmp);
	
	for(int i = 0; i < pos; i++)
	{
		for(int j = 0; j <= ans[i].len; j++)
			cout<<arr[ ans[i].brr[j]]<<' ';
		cout<<'
';
	}	
	
	cout<<pos<<endl;
	
	return 0; 
}