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2026-10-17 14:26:17

发布于：浙江

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#include<bits/stdc++.h>
#include <unordered_map>
using namespace std;
int n,m,mid;
using U=unsigned long long;
U ALL_ON;
vector<U> eff;
unordered_map<U,int> best;
int ans=INT_MAX;
void left(int i,int end,U mask,int cnt){
    if(i==end){
       auto it=best.find(mask);
        if(it==best.end()) best[mask]=cnt;
        else it->second=min(it->second,cnt);
        return;
    }
    left(i+1,end,mask,cnt);
    left(i+1,end,mask^eff[i],cnt+1);
}void right(int i,U mask,int cnt){
    if(i==n){
        U need=ALL_ON^mask;
        auto it=best.find(need);
        if(it!=best.end()){
            ans=min(ans,it->second+cnt);
        }
        return;
    }
    right(i+1,mask,cnt);
    right(i+1,mask^eff[i],cnt+1);
}
int main(){
    cin>>n>>m;
    eff.assign(n,0);
    for(int i=0;i<n;i++){
        eff[i]|=1ULL<<i;
    }
    for(int i=0;i<m;i++){
        int u,v;
        cin>>u>>v;
        u--,v--;
        eff[u]|=1ULL<<v;
        eff[v]|=1ULL<<u;
    }
    ALL_ON=(1ULL<<n)-1;
    mid=n/2;
    best.reserve((1ULL<<mid)*2);
    left(0,mid,0,0);right(mid,0,0);
    cout<<ans<<'\n';
    return 0;
}

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ㅤㅤㅤㅤㅤ

#include<bits/stdc++.h>
using namespace std;
int n, mid;
long long a[25];
map<long long, vector<int>> left_map;
vector<bool> good;

void genleft(int i, int end, long long diff, int mask) {
    if (i == end) {
        left_map[diff].push_back(mask);
        return;
    }
    genleft(i + 1, end, diff, mask);
    genleft(i + 1, end, diff + a[i], mask | (1 << i));
    genleft(i + 1, end, diff - a[i], mask | (1 << i));
}

void genright(int i, long long diff, int mask) {
    if (i == n) {
        if (left_map.count(-diff)) {
            vector<int>& candidates = left_map[-diff];
            for (int j = 0; j < (int)candidates.size(); j++) {
                good[candidates[j] | mask] = true;
            }
        }
        return;
    }
    genright(i + 1, diff, mask);
    genright(i + 1, diff + a[i], mask | (1 << i));
    genright(i + 1, diff - a[i], mask | (1 << i));
}

int main() {
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    mid = n / 2;
    good.assign(1 << n, false);
    genleft(0, mid, 0, 0);
    genright(mid, 0, 0);
    
    int ans = 0;
    for (int i = 1; i < (1 << n); i++) {
        if (good[i]) ans++;
    }
    cout << ans << endl;
    return 0;
}

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