算法库(三)

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1. for_each(beg,end,f ):按照f方式遍历区间

2. transform(beg,end,dest,f ):按照f方式遍历区间,将得到的结果写入dest中

void print( string strvlaue )

{

cout<<strvlaue<<"\n";

}

stringoperatorString( string strValue )

{

strValue += "1";

returnstrValue;

}

int main()

{

vector<string> vec_string;

for( int i = 0;i <= 4;++ i )

{

charch[10];

memset( ch,0,10 );

_itoa_s( i,ch,10 );

vec_string.push_back( ch );

}

//for_each(vec_string.begin(),vec_string.end(),print );

for_each(vec_string.begin(),vec_string.end(),operatorString );

for_each( vec_string.begin(),vec_string.end(),print);

vector<string> vec_insert;

transform(vec_string.begin(),vec_string.end(),back_inserter( vec_insert ),operatorString);

for_each(vec_insert.begin(),vec_insert.end(),print );

system("pause");

return0;

}

3. count:统计某元素出现的次数

class A

{

public:

A()

{

}

A( intno,string name ):iNo( no ),strName( name ){}

bool operator==( constA& a )

{

returna.strName == strName;

}

string retName()

{

returnstrName;

}

bool operator<( constA& a )

{

returniNo < a.iNo;

}

friendostream& operator<<( const ostream output,constA& a );

private:

intiNo;

string strName;

};

ostream& operator<<( ostream output,A& a )

{

returnoutput<<a.retName();

}

int main()

{

vector<A> lst_A;

A a1( 1,"22");

lst_A.push_back( a1 );

A a2( 2,"33");

lst_A.push_back( a2 );

A a3( 3,"44");

lst_A.push_back( a3 );

A a4( 4,"55");

lst_A.push_back( a4 );

A a5( 5,"66");

lst_A.push_back( a5 );

intiCount = count( lst_A.begin(),lst_A.end(),A( 0,"66") );

system("pause");

return0;

}

transform五个参数的版本:

int coll[]={ 5,4,6,7,1,2,3 };

//transform(coll,coll + 6,coll,negate<int>( ));

transform( coll,coll+ 6,coll,coll,plus<int>() );

copy( coll,coll +6,ostream_iterator<int>( cout," ") );