NYOJ:Binary String Matching(kmp)
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
輸入
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.
輸出
For each case, output a single line consist a single integer, tells how many times do B appears as a substring of A.
樣例輸入
3 11 1001110110 101 110010010010001 1010 110100010101011
樣例輸出
3 0 3
求出b字串在a支付串中出現了幾次。kmp演算法
#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\n",kmp()); } return 0; }