Segment Occurrences(string find函数)

Description

You are given two strings s and t, both consisting only of lowercase Latin letters.The substring s[l..r] is the string which is obtained by taking characters sl,sl+1,…,sr without changing the order.
Each of the occurrences of string a in a string b is a position i (1≤i≤|b|−|a|+1) such that b[i..i+|a|−1]=a (|a| is the length of string a).
You are asked q queries: for the i-th query you are required to calculate the number of occurrences of string t in a substring s[li..ri].

Input
The first line contains three integer numbers n, m and q (1≤n,m≤103, 1≤q≤105) — the length of string s, the length of string t and the number of queries, respectively.
The second line is a string s (|s|=n), consisting only of lowercase Latin letters.

The third line is a string t (|t|=m), consisting only of lowercase Latin letters.

Each of the next q lines contains two integer numbers li and ri (1≤li≤ri≤n) — the arguments for the i-th query.

Output

Print q lines — the i-th line should contain the answer to the i-th query, that is the number of occurrences of string t in a substring s[li..ri].

Sample Input
Input

10 3 4
codeforces
for
1 3
3 10
5 6
5 7

Output

0
1
0
1

Input

15 2 3
abacabadabacaba
ba
1 15
3 4
2 14

Output

4
0
3

Input

3 5 2
aaa
baaab
1 3
1 1

Output

0
0

Hint

In the first example the queries are substrings: "cod", "deforces", "fo" and "for", respectively.

题目意思:给出一条母串,给出一条子串,查询母串的某一个区间,问该区间有多少条子串。

解题思路:我是用string中的find来做的,find可以有两个参数,一个是子串,一个是在母串中的位置,也就是开始查询的位置,先利用find找到所有子串的起始位置,相当于打了一张表,之后查询区间,就是访问该区间中合法的子串起始位置的数量,注意子串的长度+起始位置不能越界!

 #include<cstdio>
#include<cstring>
#include<string>
#include<iostream>
#include<algorithm>
using namespace std;
int main()
{
int n,m,q,i,j,l,r,len;
int counts;
int vis[];
string s1,s2;
cin>>n>>m>>q;
cin>>s1>>s2;
len=s2.size();
memset(vis,,sizeof(vis));
string::size_type pos=;
while((pos=s1.find(s2,pos))!=string::npos)
{
vis[pos+]=pos+;
pos++;
}///打表标记母串中出现子串的位置
for(i=;i<=q;i++)
{
counts=;
scanf("%d%d",&l,&r);
for(j=l;j<=r;j++)
{
if(vis[j]!=&&vis[j]+len-<=r)///查询区间内出现子串并且不会越界
{
counts++;
}
}
printf("%d\n",counts);
}
return ;
}
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