STLalgorithm算法replace,replace_if和replace_copy,replace_copy_if(49)
replace原型:
std::replace
template <class ForwardIterator, class T>
void replace (ForwardIterator first, ForwardIterator last,
const T& old_value, const T& new_value);
将范围内的某个值替换成一个新值。
行为类似于:
template <class ForwardIterator, class T> void replace (ForwardIterator first, ForwardIterator last, const T& old_value, const T& new_value) { while (first!=last) { if (*first == old_value) *first=new_value; ++first; } }
replace_if原型:
std::replace_if
template <class ForwardIterator, class UnaryPredicate, class T> void replace_if (ForwardIterator first, ForwardIterator last, UnaryPredicate pred, const T& new_value );
将pred返回值为true的元素的值替换成new_value
行为类似于:
template < class ForwardIterator, class UnaryPredicate, class T > void replace_if (ForwardIterator first, ForwardIterator last, UnaryPredicate pred, const T& new_value) { while (first!=last) { if (pred(*first)) *first=new_value; ++first; } }
两者合成一个简单的例子:
#include <iostream> #include <algorithm> #include <vector> using namespace std; void replaceif() { vector<int> vi{1,2,3,4,4,6}; vector<int> v2{1,2,3,4,5,6}; cout<<"vi="; for(int i:vi) cout<<i<<" "; cout<<endl; cout<<"v2="; for(int i:v2) cout<<i<<" "; cout<<endl; cout<<"vi.size()="<<vi.size()<<endl; cout<<"v2.size()="<<v2.size()<<endl; replace(vi.begin(),vi.end(),4,888); cout<<"after replace(vi.begin(),vi.end(),4,888);"<<endl; cout<<"vi="; for(int i:vi) cout<<i<<" "; cout<<endl; replace_if(v2.begin(),v2.end(),[](int n){return n%2==0;},999); cout<<"after replace_if(v2.begin(),v2.end(),[](int n){return n%2==0;},999);"<<endl; cout<<"v2="; for(int i:v2) cout<<i<<" "; cout<<endl; cout<<"vi.size()="<<vi.size()<<endl; cout<<"v2.size()="<<v2.size()<<endl; }
运行截图:
replace_copy原型:
std::replace_copy
template <class InputIterator, class OutputIterator, class T> OutputIterator replace_copy (InputIterator first, InputIterator last, OutputIterator result, const T& old_value, const T& new_value);
将范围[first,last)内的元素逐一复制到result开始的位置,其中如果有元素值为old_valus,则将其值替换成new_value.
返回值为最后一个被覆盖元素的下一个位置的迭代器。
其行为类似于:
template <class InputIterator, class OutputIterator, class T> OutputIterator replace_copy (InputIterator first, InputIterator last, OutputIterator result, const T& old_value, const T& new_value) { while (first!=last) { *result = (*first==old_value)? new_value: *first; ++first; ++result; } return result; }
replace_copy_if原型:
std::replace_copy_if
template <class InputIterator, class OutputIterator, class UnaryPredicate, class T> OutputIterator replace_copy_if (InputIterator first, InputIterator last, OutputIterator result, UnaryPredicate pred, const T& new_value);
将范围[first,last)内的元素逐一复制到result开始的位置,其中如果有元素的pred返回值为ture,则将其值替换成new_value.
返回值为最后一个被覆盖元素的下一个位置的迭代器。
其行为类似于:
template <class InputIterator, class OutputIterator, class UnaryPredicate, class T> OutputIterator replace_copy_if (InputIterator first, InputIterator last, OutputIterator result, UnaryPredicate pred, const T& new_value) { while (first!=last) { *result = (pred(*first))? new_value: *first; ++first; ++result; } return result; }
两者合成一个简单的例子:
#include <iostream> #include <algorithm> #include <vector> using namespace std; void replacecopyif() { vector<int> vi{1,2,3,4,4,6}; vector<int> vresult1(6); vector<int> vresult2(6); cout<<"vi="; for(int i:vi) cout<<i<<" "; cout<<endl; cout<<"vreult1="; for(int i:vresult1) cout<<i<<" "; cout<<endl; cout<<"vreult2="; for(int i:vresult2) cout<<i<<" "; cout<<endl; replace_copy(vi.begin(),vi.end(),vresult1.begin(),4,888); cout<<"after replace(vi.begin(),vi.end(),vresult1.begin(),4,888);"<<endl; cout<<"vresult1="; for(int i:vresult1) cout<<i<<" "; cout<<endl; replace_copy_if(vi.begin(),vi.end(),vresult2.begin(),[](int n){return n%2==0;},999); cout<<"after replace_if(v2.begin(),v2.end(),vresult2.begin(),[](int n){return n%2==0;},999);"<<endl; cout<<"vresult2="; for(int i:vresult2) cout<<i<<" "; cout<<endl; }
运行截图:
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//写的错误或者不好的地方请多多指导,可以在下面留言或者点击左上方邮件地址给我发邮件,指出我的错误以及不足,以便我修改,更好的分享给大家,谢谢。
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author:天下无双
Email:coderguang@gmail.com
2014-9-25
于GDUT
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