std::remove, std::remove_if in c++
std :: remove
It is defined in <algorithm> library. It removes value from range. Transforms the range [first,last) into a range with all the elements that compare equal to val removed, and returns an iterator to the new end of that range.
- The function cannot alter the properties of the object containing the range of elements (i.e., it cannot alter the size of an array or a container).
- The relative order of the elements not removed is preserved, while the elements between the returned iterator and last are left in a valid but unspecified state.
- The function uses operator== to compare the individual elements to val.
Function Template :
ForwardIterator remove (ForwardIterator first, ForwardIterator last, const T& val) first,last : The range used is [first,last), which contains all the elements between first and last, including the element pointed by first but not the element pointed by last. val : Value to be removed. Return value : An iterator to the element that follows the last element not removed. The range between first and this iterator includes all the elements in the sequence that do not compare equal to val.
Input : 10 20 30 30 20 10 10 20 Output : 10 30 30 10 10 // Value removed is 20.
std :: remove_if
Transforms the range [first,last) into a range with all the elements for which pred returns true removed, and returns an iterator to the new end of that range.
Function Template :
ForwardIterator remove_if (ForwardIterator first, ForwardIterator last, UnaryPredicate pred); pred Unary function that accepts an element in the range as argument, and returns a value convertible to bool. The value returned indicates whether the element is to be removed (if true, it is removed). The function shall not modify its argument. This can either be a function pointer or a function object.
Input : 1 2 3 4 5 6 7 8 9 10 Output : 2 4 6 8 10 // Odd elements removed.
Original vector : 10 20 30 30 20 10 10 20 After remove : 10 30 30 10 10 Original vector : 1 2 3 4 5 6 7 8 9 10 After remove_if : 2 4 6 8 10
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