HDU 多校 6625 three arrays

http://acm.hdu.edu.cn/showproblem.php?pid=6625

题意很简单不说了。

直接说怎么做，首先建两颗字典树，把a和b数组都放进去。

然后想了想是贪心，然后想了很多比如dfs还写了很久，最后是选择了对两颗字典树同时进行BFS.

分为四个方向，两颗树都是1，两颗树都是0，一颗0一颗1，一颗1一颗0.

这四个方向，优先满足1和0；

然后这个可能写着巨麻烦，我写错了很多发。。。。。其实先前有一个稍微简单的就可以过，但不过还是有点不安全。

首先来一个看着容易一点，感觉有一点不安全的代码

#include "bits/stdc++.h"

using namespace std;
const double eps = 1e-6;
#define reg register
#define lowbit(x) x&-x
#define pll pair<ll,ll>
#define pii pair<int,int>
#define fi first
#define se second
#define makp make_pair
#define cp complex<double>

int dcmp(double x) {
    if (fabs(x) < eps) return 0;
    return (x > 0) ? 1 : -1;
}

typedef long long ll;
typedef unsigned long long ull;
const ull hash1 = 201326611;
const ull hash2 = 50331653;
const ll N = 3300000 + 10;
const int M = 1000000;
const int inf = 0x3f3f3f3f;
const ll mod = 998244353;
const double PI = acos(-1.0);
struct Trie {
    int nxt[N][2], cnt[N * 2], tot, root;
    void init() {
        tot = 1, root = 1;
        nxt[root][0] = nxt[root][1] = 0;
        cnt[root] = 0;
    }
    void Insert(int x) {
        int u = root;
        cnt[u]++;
        for (int i = 31; i >= 0; i--) {
            int idx = (x >> i) & 1;
            if (nxt[u][idx] == 0) {
                nxt[u][idx] = ++tot;
                nxt[tot][1] = nxt[tot][0] = 0;
                cnt[tot] = 0;
            }
            u = nxt[u][idx];
            cnt[u]++;
        }
    }
} ta, tb;
int n, a[N], b[N];
vector<ll> v;
struct node {
    int l, r, cnt, dep;
    ll val;
};

queue<node> qu;
void bfs() {
    while (!qu.empty()) qu.pop();
    qu.push(node{1, 1, n, 0, 0});
    while (!qu.empty()) {
        node now = qu.front();
        qu.pop();
        if (now.dep == 32) {
            for (int i = 1; i <= now.cnt; i++) {
                v.push_back(now.val);
            }
            continue;
        }
        int la = ta.nxt[now.l][0];
        int ra = ta.nxt[now.l][1];
        int lb = tb.nxt[now.r][0];
        int rb = tb.nxt[now.r][1];
        int cnt = min(ta.cnt[la], tb.cnt[lb]);
        if (cnt != 0 && la != 0 && lb != 0) {
            ta.cnt[la] -= cnt;
            tb.cnt[lb] -= cnt;
            qu.push(node{la, lb, cnt, now.dep + 1, now.val});
        }
        cnt = min(ta.cnt[ra], tb.cnt[rb]);
        if (cnt != 0 && ra != 0 && rb != 0) {
            ta.cnt[ra] -= cnt;
            tb.cnt[rb] -= cnt;
            qu.push(node{ra, rb, cnt, now.dep + 1, now.val});
        }
        cnt = min(ta.cnt[la], tb.cnt[rb]);
        if (cnt != 0 && la != 0 && rb != 0) {
            ta.cnt[la] -= cnt;
            tb.cnt[rb] -= cnt;
            ll val = now.val | (1LL << (31 - now.dep));
            qu.push(node{la, rb, cnt, now.dep + 1, val});
        }
        cnt = min(ta.cnt[ra], tb.cnt[lb]);
        if (cnt != 0 && ra != 0 && lb != 0) {
            ta.cnt[ra] -= cnt;
            tb.cnt[lb] -= cnt;
            ll val = now.val | (1LL << (31 - now.dep));
            qu.push(node{ra, lb, cnt, now.dep + 1, val});
        }
    }
}

int main() {
    int T;
    scanf("%d", &T);
    while (T--) {
        ta.init(), tb.init();
        v.clear();
        scanf("%d", &n);
        for (int i = 1; i <= n; i++) {
            scanf("%d", &a[i]);
            ta.Insert(a[i]);
        }
        for (int i = 1; i <= n; i++) {
            scanf("%d", &b[i]);
            tb.Insert(b[i]);
        }
        bfs();
        sort(v.begin(), v.end());
        cout << v[0];
        for (int i = 1; i < v.size(); i++) {
            printf(" %lld", v[i]);
        }
        printf("\n");
    }
    return 0;
}

接下来就是一个巨恶心的代码。

#include "bits/stdc++.h"

using namespace std;
const double eps = 1e-6;
#define reg register
#define lowbit(x) x&-x
#define pll pair<ll,ll>
#define pii pair<int,int>
#define fi first
#define se second
#define makp make_pair
#define cp complex<double>

int dcmp(double x) {
    if (fabs(x) < eps) return 0;
    return (x > 0) ? 1 : -1;
}

typedef long long ll;
typedef unsigned long long ull;
const ull hash1 = 201326611;
const ull hash2 = 50331653;
const ll N = 6000000 + 10;
const int M = 1000000;
const int inf = 0x3f3f3f3f;
const ll mod = 998244353;
const double PI = acos(-1.0);
struct Trie {
    int nxt[N][2], cnt[N * 2], tot, root;
    void init() {
        tot = 1;
        root = newnode();
    }
    int newnode() {
        nxt[tot][0] = nxt[tot][1] = 0;
        cnt[tot] = 1;
        return tot++;
    }
    void Insert(int x) {
        int u = root;
        cnt[u]++;
        for (int i = 29; i >= 0; i--) {
            int idx = (x >> i) & 1;
            if (nxt[u][idx] == 0) {
                nxt[u][idx] = newnode();
            } else {
                cnt[nxt[u][idx]]++;
            }
            u = nxt[u][idx];
        }
    }
} ta, tb;
int n, a[N], b[N];
vector<ll> v;
struct node {
    int l, r, cnt, dep;
    ll val;
};
void bfs(int n) {
    queue<node> qu;
    qu.push(node{1, 1, n, 0, 0});
    while (!qu.empty()) {
        node now = qu.front();
        qu.pop();
        if (now.dep == 30) {
            for (int i = 1; i <= now.cnt; i++) {
                v.push_back(now.val);
            }
            continue;
        }
        int cnt = now.cnt;
        int la = ta.nxt[now.l][0];
        int ra = ta.nxt[now.l][1];
        int lb = tb.nxt[now.r][0];
        int rb = tb.nxt[now.r][1];
        int nla = ta.cnt[la];
        int nlb = tb.cnt[lb];
        int nra = ta.cnt[ra];
        int nrb = tb.cnt[rb];
        int cnt00 = min(cnt, min(nla, nlb));
        cnt -= cnt00;
        int cnt11 = min(cnt, min(nra, nrb));
        cnt -= cnt11;
        nla -= cnt00;
        nlb -= cnt00;
        nra -= cnt11;
        nrb -= cnt11;
        if (cnt00) {
            qu.push(node{la, lb, cnt00, now.dep + 1, now.val});
        }
        if (cnt11) {
            qu.push(node{ra, rb, cnt11, now.dep + 1, now.val});
        }
        int cnt01 = min(cnt, min(nla, nrb));
        cnt -= cnt01;
        int cnt10 = min(cnt, min(nra, nlb));
        cnt -= cnt10;
        nla -= cnt01;
        nlb -= cnt10;
        nra -= cnt10;
        nrb -= cnt01;
        if (cnt01) {
            ll val = now.val | (1LL << (29 - now.dep));
            qu.push(node{la, rb, cnt01, now.dep + 1, val});
        }
        if (cnt10) {
            ll val = now.val | (1LL << (29 - now.dep));
            qu.push(node{ra, lb, cnt10, now.dep + 1, val});
        }
        ta.cnt[la] = nla;
        ta.cnt[ra] = nra;
        tb.cnt[lb] = nlb;
        tb.cnt[rb] = nrb;
    }
}

int main() {
    int T;
    scanf("%d", &T);
    ///cin >> T;
    while (T--) {
        ta.init(), tb.init();
        v.clear();
        scanf("%d", &n);
        ///cin >> n;
        for (int i = 1; i <= n; i++) {
            scanf("%d", &a[i]);
            ///cin >> a[i];
            ta.Insert(a[i]);
        }
        for (int i = 1; i <= n; i++) {
            scanf("%d", &b[i]);
            ///cin >> b[i];
            tb.Insert(b[i]);
        }
        bfs(n);
        sort(v.begin(), v.end());
        ///printf("%d", v[0]);
        cout << v[0];
        for (int i = 1; i < v.size(); i++) {
            ///printf(" %d", v[i]);
            cout << " " << v[i];
        }
        ///printf("\n");
        cout << endl;
    }
    return 0;
}