# @atcoder - AGC024F@ Simple Subsequence Problem

## @accepted code@

#include <cstdio>

int ch[2][1<<22], id[22][1<<21], cnt;
void get() {
id[0][0] = (cnt++), ch[0][id[0][0]] = ch[1][id[0][0]] = -1;
for(int i=1;i<=20;i++) {
int t = (1 << i), k = (t >> 1);
for(int s=0;s<t;s++) {
id[i][s] = (cnt++);
int p = (s & k), q = (p ? 1 : 0);
ch[q][id[i][s]] = id[i-1][s^p];
ch[!q][id[i][s]] = ch[!q][id[i-1][s^p]];
}
}
}

int a[22][1<<22], siz[22], c[22][1<<22], num[22][1<<22];

int ans[22], N, K;
void dfs(int d, int s) {
if( ans[d] == -1 ) ans[d] = s;
for(int p=0;p<=1;p++) {
int tot = 0;
for(int i=0;i<siz[d];i++) {
int to = ch[p][a[d][i]];
if( to == -1 ) continue;
if( num[d + 1][to] == -1 )
num[d + 1][a[d + 1][siz[d + 1]] = to] = siz[d + 1], siz[d + 1]++;
tot += c[d][i], c[d + 1][num[d + 1][to]] += c[d][i];
}
if( tot >= K ) dfs(d + 1, (s << 1) | p);
for(int i=0;i<siz[d + 1];i++)
num[d + 1][a[d + 1][i]] = -1, c[d + 1][i] = 0;
siz[d + 1] = 0;
}
}

char s[1<<21];
int main() {
scanf("%d%d", &N, &K), get();
for(int i=0;i<=N;i++)
for(int j=0;j<cnt;j++)
num[i][j] = -1;
for(int i=0;i<=N;i++) {
scanf("%s", s);
int t = (1 << i);
for(int j=0;j<t;j++) {
if( s[j] == '1' )
num[0][a[0][siz[0]] = id[i][j]] = siz[0], c[0][num[0][id[i][j]]]++, siz[0]++;
}
ans[i] = -1;
}
dfs(0, 0);
for(int i=N;i>=0;i--) {
if( ans[i] != -1 ) {
for(int j=i-1;j>=0;j--)
putchar(((ans[i] >> j) & 1) + '0');
puts(""); return 0;
}
}
}


## @details@

posted @ 2020-01-19 09:02  Tiw_Air_OAO  阅读(208)  评论(0编辑  收藏