Count the string
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 4842 Accepted Submission(s): 2293
Problem Description
It is well known that AekdyCoin is good at string problems as well as number theory problems. When given a string s, we can write down all the non-empty prefixes of this string. For example:
s: "abab"
The prefixes are: "a", "ab", "aba", "abab"
For each prefix, we can count the times it matches in s. So we can see that prefix "a" matches twice, "ab" matches twice too, "aba" matches once, and "abab" matches once. Now you are asked to calculate the sum of the match times for all the prefixes. For "abab",
it is 2 + 2 + 1 + 1 = 6.
The answer may be very large, so output the answer mod 10007.
s: "abab"
The prefixes are: "a", "ab", "aba", "abab"
For each prefix, we can count the times it matches in s. So we can see that prefix "a" matches twice, "ab" matches twice too, "aba" matches once, and "abab" matches once. Now you are asked to calculate the sum of the match times for all the prefixes. For "abab",
it is 2 + 2 + 1 + 1 = 6.
The answer may be very large, so output the answer mod 10007.
Input
The first line is a single integer T, indicating the number of test cases.
For each case, the first line is an integer n (1 <= n <= 200000), which is the length of string s. A line follows giving the string s. The characters in the strings are all lower-case letters.
For each case, the first line is an integer n (1 <= n <= 200000), which is the length of string s. A line follows giving the string s. The characters in the strings are all lower-case letters.
Output
For each case, output only one number: the sum of the match times for all the prefixes of s mod 10007.
Sample Input
1 4 abab
Sample Output
6
/*
题目要求求：字串的前缀个数+与前缀相同的子串个数
字串的前缀个数当然就是整个串的长度了，
与前缀相同的子串个数 就是KMP求得的fun函数（部分匹配函数）
fun[i]表示前缀等于后缀的最大长度，说明有
2
4
abab
12
abcabacbabca
*/
#include<iostream>
#include<stdio.h>
using namespace std;
char target[10001],str[1000001];
void cal(char s[],int fun[])
{
int len,LOLP,i,L;
len=strlen(s);
L=0;//最长前缀
fun[1]=0;
for(i=2;i<=len;i++)
{
while(L>0 && (s[L]!=s[i-1]))
L=fun[L];
if(s[L]==s[i-1])
L++;
fun[i]=L;
}
}
int main()
{
int i,t,sum,n,fun[200001];
// freopen("test.txt","r",stdin);
scanf("%d",&t);
while(t--)
{
scanf("%d",&n);
scanf("%s",target);
cal(target,fun);
sum=0;
for(i=1;i<=n;i++)
{
if(fun[i]!=0)
sum++;
if(sum>10007)
sum=sum%10007;
}
sum+=n;
sum=sum%10007;
printf("%d\n",sum);
}
return 0;
}