codeforces 1118C

codeforces 1118C

矩阵是否中心对称

偶数直接判断每个数的个数是否恰为4的倍数

奇数，计算余为1和3的个数，有且仅有一个才可能成为中心。余为2的个数不因大于N - 1（减去中心）

#include
using namespace std;
#define fst first
#define sec second
#define sci(num) scanf("%d",&num)
#define scl(num) scanf("%lld",&num)
#define mem(a,b) memset(a,b,sizeof a)
#define cpy(a,b) memcopy(a,b,sizeof b)
typedef long long LL;
typedef pair P;
const int MAX_N = 1e5 + 100;
const int MAX_M  = 310;
int mtx[410][410];
int a[1010];
struct e{
    int num,cnt;
    bool operator<(e& e1) {
        if (this->cnt  != e1.cnt ) return this->cnt  > e1.cnt ;
        return this->num < e1.num;
    }
} e[1010];
int main() {
    ios::sync_with_stdio(false); cin.tie(0);
    int N;
    cin >> N;
    for (int i = 1;i <= 1000;i++)
        e[i].num = i;
    for (int i = 1;i <= N * N;i++) {
        cin >> a[i];
        e[a[i]].cnt++;
    }

    if (N == 1) {
        cout << "YES" << endl;
        cout << a[1] << endl;
    } else {
        sort(e + 1,e + 1001);
        int cnt = 1;
        for (;e[cnt].cnt;cnt++)
            ;
        cnt--;
        int len = N;
        if (len % 2 == 1) {
            bool flag = true;
            int cnt1 = 0; int loc = -1;
            int cnt2 = 0;
            int cnt3 = 0;
            for (int i = 1;i <= cnt;i++) {
                if (e[i].cnt % 4 == 1) {
                    cnt1++;
                    loc = i;
                } else if (e[i].cnt % 4 == 2) {
                    cnt2++;
                } else if (e[i].cnt % 4 == 3) {
                    cnt3++;
                    loc = i;
                }
            }
            int cnt4 = cnt - cnt1 - cnt2 - cnt3;
            if (cnt1 + cnt3 != 1) flag =false;
            mtx[len/2+1][len/2+1] = e[loc].num;
            e[loc].cnt--;
            if (cnt1 == 1) cnt1--,cnt4++;
            else if (cnt3 == 1) cnt3--,cnt2++;
            if (cnt2 > len - 1 || cnt2 % 2 == 1) flag = false;
            if (!flag) {
                cout << "NO" << endl;
                return 0;
            }
            int now = 1;
            for (int i = 1;i <= len / 2;i++) {
                for (int j = 1;j <= len / 2;j++) {
                    while (e[now].cnt < 4) now++;
                    mtx[i][j] = mtx[i][len - j + 1]
                            = mtx[len - i + 1][j] = mtx[len - i + 1][len - j + 1] = e[now].num;
                    e[now].cnt -= 4;
                }
            }
            int t = 1;
            for (int i  = 1;i <= len / 2;i++) {
                int j = len / 2 + 1;
                while (e[t].cnt == 0) t++;
                mtx[i][j] = mtx[len - i + 1][j] = e[t].num;
                e[t].cnt -= 2;
                while (e[t].cnt == 0) t++;
                mtx[j][len - i + 1]  = mtx[j][i] = e[t].num;
                e[t].cnt -= 2;
            }
        } else {
            bool flag = true;
            for (int i = 1;i <= cnt;i++) {
                if (e[i].cnt % 4 != 0) {
                    flag = false;
                }
            }
            if (!flag) {
                cout << "NO" << endl;
                return 0;
            }
            int now = 1;
            for (int i = 1;i <= len / 2;i++) {
                for (int j = 1;j <= len / 2;j++) {
                    while (e[now].cnt== 0) now++;
                    mtx[i][j] = mtx[i][len - j + 1]
                            = mtx[len - i + 1][j] = mtx[len - i + 1][len - j + 1] = e[now].num;
                    e[now].cnt -= 4;
                }
            }
        }
        cout << "YES" << endl;
        for (int i = 1;i <= len;i++) {
            cout << mtx[i][1];
            for (int j = 2;j <= len;j++) {
                cout << " " << mtx[i][j];
            }
            cout << endl;
        }
    }

    return 0;
}