28. Implement strStr()
Problem's Link
----------------------------------------------------------------------------
Mean:
给定两个字符串str1和str2,输出str2在str1中第一次出现的下标.
analyse:
KMP算法模板题.
Time complexity: O(N)
view code
/**
* -----------------------------------------------------------------
* Copyright (c) 2016 crazyacking.All rights reserved.
* -----------------------------------------------------------------
* Author: crazyacking
* Date : 2016-02-19-16.45
*/
#include <queue>
#include <cstdio>
#include <set>
#include <string>
#include <stack>
#include <cmath>
#include <climits>
#include <map>
#include <cstdlib>
#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
using namespace std;
typedef long long( LL);
typedef unsigned long long( ULL);
const double eps( 1e-8);
class Solution
{
public :
int Next [ 100005 ];
void getNext( string & s)
{
Next [ 0 ] = 0;
for( int i = 1 , k = 0; i <s . length(); ++ i)
{
while(s [ i ] !=s [ k ] && k)
k = Next [ k - 1 ];
if(s [ i ] ==s [ k ])
++ k;
Next [ i ] = k;
}
}
int strStr( string haystack , string needle)
{
if( needle . length() == 0)
return 0;
getNext( needle);
for( int i = 0 , k = 0; i < haystack . length(); ++ i)
{
while( haystack [ i ] != needle [ k ] && k)
k = Next [ k - 1 ];
if( haystack [ i ] == needle [ k ])
++ k;
if( k == needle . length())
return i - k + 1;
}
return - 1;
}
};
int main()
{
string str1 , str2;
while( cin >> str1 >> str2)
{
Solution solution;
cout << solution . strStr( str1 , str2) << endl;
}
return 0;
}
/*
*/
* -----------------------------------------------------------------
* Copyright (c) 2016 crazyacking.All rights reserved.
* -----------------------------------------------------------------
* Author: crazyacking
* Date : 2016-02-19-16.45
*/
#include <queue>
#include <cstdio>
#include <set>
#include <string>
#include <stack>
#include <cmath>
#include <climits>
#include <map>
#include <cstdlib>
#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
using namespace std;
typedef long long( LL);
typedef unsigned long long( ULL);
const double eps( 1e-8);
class Solution
{
public :
int Next [ 100005 ];
void getNext( string & s)
{
Next [ 0 ] = 0;
for( int i = 1 , k = 0; i <s . length(); ++ i)
{
while(s [ i ] !=s [ k ] && k)
k = Next [ k - 1 ];
if(s [ i ] ==s [ k ])
++ k;
Next [ i ] = k;
}
}
int strStr( string haystack , string needle)
{
if( needle . length() == 0)
return 0;
getNext( needle);
for( int i = 0 , k = 0; i < haystack . length(); ++ i)
{
while( haystack [ i ] != needle [ k ] && k)
k = Next [ k - 1 ];
if( haystack [ i ] == needle [ k ])
++ k;
if( k == needle . length())
return i - k + 1;
}
return - 1;
}
};
int main()
{
string str1 , str2;
while( cin >> str1 >> str2)
{
Solution solution;
cout << solution . strStr( str1 , str2) << endl;
}
return 0;
}
/*
*/