Crisp String CodeForces

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <math.h>
#include <set>
#include <map>
#include <queue>
#include <string>
#include <string.h>
#define REP(i,a,n) for(int i=a;i<=n;++i)
#define PER(i,a,n) for(int i=n;i>=a;--i)
#define hr putchar(10)
#define pb push_back
#define lc (o<<1)
#define rc (lc|1)
#define mid ((l+r)>>1)
#define ls lc,l,mid
#define rs rc,mid+1,r
#define x first
#define y second
#define io std::ios::sync_with_stdio(false)
#define endl '
'
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int P = 1e9+7, INF = 0x3f3f3f3f;
ll gcd(ll a,ll b) {return b?gcd(b,a%b):a;}
ll qpow(ll a,ll n) {ll r=1%P;for (a%=P;n;a=a*a%P,n>>=1)if(n&1)r=r*a%P;return r;}
ll inv(ll x){return x<=1?1:inv(P%x)*(P-P/x)%P;}
//head
#ifdef ONLINE_JUDGE
const int N = 1e6+10;
#else
const int N = 111;
#endif


int n, m, mx, ans = INF;
char s[N];
int a[N], tmp[1<<17], f[1<<17];
int cst[1<<17], dp[1<<17];
int g[17][17];

void dfs(int x) {
	if (tmp[x]) return;
	tmp[x] = 1;
	for (int y=x; y; y^=y&-y) dfs(x^y&-y);
}
void dfs1(int x) {
	if (f[x]||tmp[x]) return;
	tmp[x] = 1;
	ans = min(ans, cst[x]);
	for (int y=x; y; y^=y&-y) dfs1(x^y&-y);
}

int main() {
	scanf("%d%d%s", &n, &m, s+1), mx=(1<<m)-1;
	REP(i,1,n) ++cst[1<<(a[i]=s[i]-'a')];
	REP(i,1,mx) cst[i]=cst[i^i&-i]+cst[i&-i];
	REP(i,0,m-1) REP(j,0,m-1) scanf("%d", &g[i][j]);
	REP(i,0,m-1) REP(j,0,m-1) if (!g[i][j]) {
		int now = 0, pre = -1;
		REP(k,1,n) {
			if (a[k]==i||a[k]==j) {
				if (a[k]==i&&pre==j||a[k]==j&&pre==i) {
					dfs(mx^now);
				}
				now = 0, pre = a[k];
			}
			else now |= 1<<a[k];
		}
		int t = 1<<i|1<<j;
		REP(k,0,mx) { 
			if ((k&t)==t) f[k] |= tmp[k];
			tmp[k]=0;		
		}
	}
	dfs1(mx);
	printf("%d
", ans);
}