数一数(KMP)

题目链接:here

题解:首先找最短的串,长度为minlen, 可知长度更长的串答案一定为0, 而长度等于minlen的串答案相等。

其实稍微想一下就知道了,比赛的时候上来就把KMP否了,一直在想别的做法。。。一点也不知道思考啊。。。

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 #define LL long long
 4 const int maxn = 1e6 + 10;
 5 const int mod = 998244353;
 6 char s[maxn * 3];
 7 int l[maxn];
 8 int nxt[maxn * 2];
 9 
10 void getfail(char *p){
11     int len = strlen(p);
12     nxt[0] = nxt[1] = 0;
13     for(int i = 1; i < len; i++){
14         int j = nxt[i];
15         while(j && p[i] != p[j]) j = nxt[j];
16         nxt[i + 1] = p[i] == p[j] ? j + 1 : 0;
17     }
18 }
19 
20 LL kmp(char *s, char *p){
21     int lens = strlen(s), lenp = strlen(p);
22     int cnt = 0;
23     int j = 0;
24     for(int i = 0; i < lens; i++){
25         while(j && s[i] != p[j]) j = nxt[j];
26         if(s[i] == p[j]) j++;
27         if(j == lenp){
28             j = nxt[j];
29             cnt++;
30         }
31     }
32     return cnt;
33 }
34 
35 int main(){
36     int n;
37     scanf("%d", &n);
38     int minid = n, minlen = maxn * 3;
39     int pos = 0;
40     for(int i = 0; i < n; i++){
41         scanf("%s", s + pos);
42         l[i] = pos;
43         int len = strlen(&s[pos]);
44         if(minlen > len) minid = i, minlen = len;
45         pos = pos + len + 1;
46     }
47     LL ans = 1;
48     char *p = &s[l[minid]];
49     getfail(p);
50     for(int i = 0; i < n; i++) if(i != minid){
51         ans = ans * kmp(&s[l[i]], p) % mod;
52     }
53     for(int i = 0; i < n; i++) {
54         if(strlen(&s[l[i]]) == minlen) printf("%lld
", ans);
55         else puts("0");
56     }
57 
58 }
View Code
原文地址:https://www.cnblogs.com/yijiull/p/8413075.html