拆位+堆优化最短路 牛妹游历城市 牛客练习赛67

对于一道题目，如果涉及到了位运算，二进制，那么优先考虑二进制，观察其性质

本题以对点权的二进制构造边，构造32个虚点，从而建立出图

 

堆优化优先队列，一定不要出现爆LL的情况，这样极有可能MLE，TLE，因为入队次数会变得乱糟糟的

//#define LOCAL
#include 
using namespace std;
#define ll long long
#define mem(a, b) memset(a,b,sizeof(a))
#define sz(a) (int)a.size()
#define INF 0x3f3f3f3f
#define DNF 0x7f7f7f7f
#define DBG printf("this is a input\n")
#define fi first
#define se second
#define mk(a, b) make_pair(a,b)
#define pb push_back
#define LF putchar('\n')
#define SP putchar(' ')
#define p_queue priority_queue
#define CLOSE ios::sync_with_stdio(0); cin.tie(0)

template
void read(T &x) {x = 0;char ch = getchar();ll f = 1;while(!isdigit(ch)){if(ch == '-')f *= -1;ch = getchar();}while(isdigit(ch)){x = x * 10 + ch - 48; ch = getchar();}x *= f;}
template
void read(T &first, Args& ... args) {read(first);read(args...);}
template
void write(T arg) {T x = arg;if(x < 0) {putchar('-'); x =- x;}if(x > 9) {write(x / 10);}putchar(x % 10 + '0');}
template
void write(T arg, Ts ... args) {write(arg);if(sizeof...(args) != 0) {putchar(' ');write(args ...);}}
using namespace std;

const int N = 1e5 + 100;
const int M = 6400050;
const ll MAXN = (1ll << 32);
int n ;
int head[N], cnt;
ll val[N];
struct node1 {
    int t, next;
    ll w;
}edge[M];
void add (int f, int t, ll w)
{
    edge[cnt].w = w;
    edge[cnt].t = t;
    edge[cnt].next = head[f];
    head[f] = cnt ++;
}
struct node
{
    int v;
    ll value;
    node(int a, ll b):v(a),value(b){};
    bool operator < (const node& no) const {
        return value > no.value;
    }
};
ll dis[N];
void dijkstra(int s)
{
    for (int i = 0 ; i <= n + 40 ; i ++)
        dis[i] = 1e18;
    p_queue  q;
    dis[s] = 0;
    q.push(node(s,0));
    while(!q.empty())
    {
        node no = q.top();
        q.pop();
        int u = no.v;
        for(int i = head[u] ; i != -1 ; i = edge[i].next)
        {
            int v = edge[i].t;
            ll w = edge[i].w;
            if(dis[v] > dis[u] + w)
            {
                dis[v] = dis[u] + w;
                q.push(node(v,dis[v]));
            }
        }
    }
}
int main()
{
    cout << (1 << 32) << endl;
    int T;
    read (T);
    while (T --)
    {
        read (n);
        cnt = 0;
        for (int i = 1 ; i <= n + 40 ; i ++)
            head[i] = -1;
        for (int i = 1 ; i <= n ; i ++)
            read (val[i]);
        int p = n;
        for (ll t = 1 ; t < MAXN ; t <<= 1)
        {
            ++ p;
            for (int i = 1 ; i <= n ; i ++)
            {
                if(val[i] & t)
                {
                    add (i , p , t);
                    add (p , i, 0);
                }
            }
        }
        dijkstra(1);
        if(dis[n] == 1e18)
            printf("Impossible\n");
        else
            write(dis[n]), LF;
    }

}
/*
2
6 5
0 1 0 1 0 1
1 3
3 5
1 2
2 4
4 5
 */