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  • hihocoder 1015 KMP算法

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    #include<queue>
    #include<cmath>
    #include<cstdio>
    #include<cstring>
    #include<cstdlib>
    #include<iostream>
    #include<algorithm>
    #define ll long long
    #define inf 1000000000
    #define mod 1000000007
    using namespace std;
    int read()
    {
        int x=0,f=1;
        char ch=getchar();
        while(ch<'0'||ch>'9')
        {
            if(ch=='-')f=-1;
            ch=getchar();
        }
        while(ch>='0'&&ch<='9')
        {
            x=x*10+ch-'0';
            ch=getchar();
        }
        return x*f;
    }
    const int N=1e6+10;
    int f[N];
    char a[N],b[N];
    void getFail(int m)
    {
        f[1]=0;
        int j=f[1];
        for(int i=2; i<=m; i++)
        {
            while(j>0&&b[i]!=b[j+1]) j=f[j];
            if(b[i]==b[j+1]) j++;
            f[i]=j;
        }
    }
    int find(int n,int m)
    {
        int i,j=0,cnt=0;
        for(i=1; i<=n; i++)
        {
            while(j>0&&b[j+1]!=a[i]) j=f[j];
            if(b[j+1]==a[i]) j+=1;
            if(j==m)
            {
                cnt++;
            }
        }
        return cnt;
    }
    int main()
    {
        int n=read();
        int m=2*n;
        for(int i=0;i<n;i++){
            scanf("%s %s",b+1,a+1);
            getFail(strlen(b+1));
            printf("%d
    ",find(strlen(a+1),strlen(b+1)));
        }
        return 0;
    }
    
    
    #include<queue>
    #include<cmath>
    #include<cstdio>
    #include<cstring>
    #include<cstdlib>
    #include<iostream>
    #include<algorithm>
    #define ll long long
    #define inf 1000000000
    #define mod 1000000007
    using namespace std;
    int read()
    {
        int x=0,f=1;
        char ch=getchar();
        while(ch<'0'||ch>'9')
        {
            if(ch=='-')f=-1;
            ch=getchar();
        }
        while(ch>='0'&&ch<='9')
        {
            x=x*10+ch-'0';
            ch=getchar();
        }
        return x*f;
    }
    const int N=1e6+10;
    int f[N];
    char a[N],b[N];
    void get_next(){
        int j=0,k=-1;
        f[0]=-1;
        int m=strlen(b);
        while(j<m){
            if(k==-1||b[j]==b[k]) f[++j]=++k;
            else k=f[k];
        }
    }
    int kmp_count(){
        int n=strlen(a),m=strlen(b);
        int i=0,j=0,res=0;
        while(i<n){
            if(j==-1||a[i]==b[j]) i++,j++;
            else j=f[j];
            if(j==m){
                res++;
                j=f[j];
            }
        }
        return res;
    }
    int main(){
        int T=read();
        while(T--) {
            scanf("%s%s",b,a);
            get_next();
            printf("%d
    ",kmp_count());
        }
        return 0;
    }
    
    #include <queue>
    #include <cmath>
    #include <cstdio>
    #include <cstring>
    #include <cstdlib>
    #include <iostream>
    #include <algorithm>
    #include <vector>
    #define ll long long
    #define inf 1000000000000000LL
    #define mod 1000000007
    using namespace std;
    int read()
    {
        int x=0,f=1;
        char ch=getchar();
        while(ch<'0'||ch>'9')
        {
            if(ch=='-')f=-1;
            ch=getchar();
        }
        while(ch>='0'&&ch<='9')
        {
            x=x*10+ch-'0';
            ch=getchar();
        }
        return x*f;
    }
    const int N=1e6+10;
    char a[N],b[N];
    int f[N];
    void get_next(){
        int m=strlen(b);
        f[0]=f[1]=0;
        for(int i=1;i<m;i++){
            int j=f[i];
            while(j&&b[i]!=b[j]) j=f[j];
            f[i+1]=b[i]==b[j]?j+1:0;
        }
    }
    int kmp_count(){
        int n=strlen(a),m=strlen(b);
        int j=0,res=0;
        for(int i=0;i<n;i++){
            while(j&&b[j]!=a[i]) j=f[j];
            if(b[j]==a[i]) j++;
            if(j==m){
                res++;
                j=f[j];
                if(j>m) j=0;
            }
        }
        return res;
    }
    int main(){
        int n=read();
        while(n--) {
            scanf("%s%s",b,a);
            get_next();
            printf("%d
    ",kmp_count());
        }
        return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/zsyacm666666/p/6740645.html
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