http://acm.nyist.edu.cn/JudgeOnline/problem.php?pid=5
描述
Given two strings A and B, whose alphabet consist only ‘0’ and ‘1’. Your task is only to tell how many times does A appear as a substring of B? For example, the text string B is ‘1001110110’ while the pattern string A is ‘11’, you should output 3, because the pattern A appeared at the posit
输入
The first line consist only one integer N, indicates N cases follows. In each case, there are two lines, the first line gives the string A, length (A) <= 10, and the second line gives the string B, length (B) <= 1000. And it is guaranteed that B is always longer than A.
输出
For each case, output a single line consist a single integer, tells how many times do B appears as a substring of A.
样例输入
3 11 1001110110 101 110010010010001 1010 110100010101011
样例输出
3 0 3
求出b字符串在a支付串中出现了几次。kmp算法
#include<stdio.h>
#include<string.h>
#define N 1020
int next[N],len1,len2;
char a[N],b[N];
void get_next()
{
int i=0,j=-1;
next[0]=-1;
while(i<len2)
{
if(b[i]==b[j]||j==-1)
{
i++;
j++;
next[i]=j;
}
else
j=next[j];
}
}
int kmp()
{
int ans=0;
get_next();
int i=0,j=0;
while(i<len1)
{
if(a[i]==b[j]||j==-1)
{
i++;
j++;
}
else
j=next[j];
if(j>=len2)
{
ans++;
j=next[j];
}
}
return ans;
}
int main()
{
int t;
scanf("%d",&t);
while(t--)
{
scanf("%s%s",b,a);
memset(next,0,sizeof(next));
len1=strlen(a);
len2=strlen(b);
printf("%d
",kmp());
}
return 0;
}