codeforces 535D. Tavas and Malekas KMP

题目链接

又复习了一遍kmp....之前都忘光了

#include<bits/stdc++.h>
using namespace std;
#define pb(x) push_back(x)
#define ll long long
#define mk(x, y) make_pair(x, y)
#define lson l, m, rt<<1
#define mem(a) memset(a, 0, sizeof(a))
#define rson m+1, r, rt<<1|1
#define mem1(a) memset(a, -1, sizeof(a))
#define mem2(a) memset(a, 0x3f, sizeof(a))
#define rep(i, a, n) for(int i = a; i<n; i++)
#define ull unsigned long long
typedef pair<int, int> pll;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int mod = 1e9+7;
const int inf = 1061109567;
const int dir[][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };
const int maxn = 1e6+5;
int next[maxn], a[maxn], vis[maxn], used[maxn];
char s[maxn];
void get_next() {
    int len = strlen(s);
    int i = 0, j = -1;
    next[0] = -1;
    while(i<len) {
        if(j==-1 || s[i] == s[j]) {
            i++, j++;
            next[i] = j;
        } else {
            j = next[j];
        }
    }
    int pos = next[len];
    while(pos != -1) {
        vis[pos] = 1;
        pos = next[pos];
    }
    return ;
}
int main()
{
    int n, m;
    cin>>n>>m;
    scanf("%s", s);
    int len = strlen(s);
    get_next();
    for(int i = 1; i<=m; i++) {
        scanf("%d", &a[i]);
    }
    sort(a+1, a+m+1);
    int flag = 0;
    for(int i = 1; i<=m; i++) {
        if(i == 1 || a[i]-a[i-1]>len) {
            for(int j = a[i]; j<len+a[i]; j++) {
                used[j] = 1;
            }
        } else {
            if(vis[len+a[i-1]-a[i]]) {
                for(int j = a[i-1]+len; j<len+a[i]; j++) {
                    used[j] = 1;
                }
            } else {
                flag = 1;
                break;
            }
        }
    }
    if(flag) {
        puts("0");
        return 0;
    }
    ll ans = 1;
    for(int i = 1; i<=n; i++) {
        if(!used[i]) {
            ans = (ans*26)%mod;
        }
    }
    cout<<ans<<endl;
    return 0;
}