Codeforces Round #454 D. Seating of Students

#include<iostream>
#include<map>
#include<iostream>
#include<cstring>
#include<cstdio>
#include<set>
#include<vector>
#include<queue>
#include<cmath>
#include<stack>
#include<algorithm>
using namespace std;
typedef long long ll;
const int N = 1e5 + 5;
#define MS(x,y) memset(x,y,sizeof(x))
#define MP(x, y) make_pair(x, y)
const int INF = 0x3f3f3f3f;

map<pair<int, int>, int> mp;
int vc
;

int main() {
int n, m;
while(~scanf("%d %d", &n, &m)) {
mp.clear();
for(int i = 0; i < n; ++i) {
for(int j = 0; j < m; ++j) {
mp[MP(i, j)] = i*m + j;
}
}

if(n == 1 && m == 1) {
printf("YES\n1\n");
}else if(n == 3 && m == 3) {
printf("YES\n");
printf("6 1 8\n7 5 3\n2 9 4\n");
}else if(n >= 4) {
printf("YES\n");
for(int i = 0; i < m; ++i) {
int cnt = 0;
for(int j = 0; j < n; ++j) {
vc[cnt ++] = mp[MP(j, i)];
}
if(n == 4) {
if(i & 1) { mp[MP(0, i)] = vc[2]; mp[MP(1, i)] = vc[0]; mp[MP(2, i)] = vc[3]; mp[MP(3, i)] = vc[1]; }
else      { mp[MP(0, i)] = vc[1]; mp[MP(1, i)] = vc[3]; mp[MP(2, i)] = vc[0]; mp[MP(3, i)] = vc[2]; }
continue;
}
int tt = 0;
if(i & 1) {
for(int j = 0; j < cnt; j += 2) mp[MP(tt++, i)] = vc[j];
for(int j = 1; j < cnt; j += 2) mp[MP(tt++, i)] = vc[j];
}else {
for(int j = 1; j < cnt; j += 2) mp[MP(tt++, i)] = vc[j];
for(int j = 0; j < cnt; j += 2) mp[MP(tt++, i)] = vc[j];

}
}
for(int i = 0; i < n; ++i) {
for(int j = 0; j < m; ++j) printf("%d ", mp[MP(i, j)] + 1);
printf("\n");
}
}else if(m >= 4) {
printf("YES\n");
for(int i = 0; i < n; ++i) {
int cnt = 0;
for(int j = 0; j < m; ++j) {
vc[cnt ++] = mp[MP(i, j)];
}
if(m == 4) {
if(i & 1) { mp[MP(i, 0)] = vc[2]; mp[MP(i, 1)] = vc[0]; mp[MP(i, 2)] = vc[3]; mp[MP(i, 3)] = vc[1]; }
else      { mp[MP(i, 0)] = vc[1]; mp[MP(i, 1)] = vc[3]; mp[MP(i, 2)] = vc[0]; mp[MP(i, 3)] = vc[2]; }
continue;
}
int tt = 0;
if(i & 1) {
for(int j = 0; j < cnt; j += 2) mp[MP(i, tt++)] = vc[j];
for(int j = 1; j < cnt; j += 2) mp[MP(i, tt++)] = vc[j];
}
else {
for(int j = 1; j < cnt; j += 2) mp[MP(i, tt++)] = vc[j];
for(int j = 0; j < cnt; j += 2) mp[MP(i, tt++)] = vc[j];
}
}
for(int i = 0; i < n; ++i) {
for(int j = 0; j < m; ++j) printf("%d ", mp[MP(i, j)] + 1);
printf("\n");
}
}else printf("NO\n");
}
return 0;
}