forward list是一个行为受限的list, 不能走回头路。
它只提供前向迭代器, 而不提供双向迭代器。
eg:
rbegin(), rend(), crbegin(), crend()这些都不提供。
它不提供size()成员函数。
没有指向最末元素的anchor， 因此不提供back(), push_back(), pop_back()。
ForwardListTest.cpp:
#include <forward_list> #include "../../Core/print.hpp" #include "ForwardListTest.h" using namespace std; void ForwardListTest::findDemo() { forward_list<int> list = { 1, 2, 3, 4, 5, 97, 98, 99 }; // find the position before the first even element auto posBefore = list.before_begin(); for (auto pos = list.begin(); pos != list.end(); ++pos, ++posBefore) { if (*pos % 2 == 0) { break; // element found } } // and insert a new element in front of the first even element list.insert_after(posBefore, 42); PRINT_ELEMENTS(list); } void ForwardListTest::run() { printStart("findDemo()"); findDemo(); printEnd("findDemo()"); }
运行结果:
---------------- findDemo(): Run Start ----------------
1 42 2 3 4 5 97 98 99
---------------- findDemo(): Run End ----------------
自定义find_before_if操作：
#include "../../Core/findbefore.hpp" void ForwardListTest::findBeforeDemo() { forward_list<int> list = { 1, 2, 3, 4, 5, 97, 98, 99 }; // find the position before the first even element auto posBefore = find_before_if(list.before_begin(), list.end(), [](int i) { return i % 2 == 0; }); // and insert a new element in front of the first even element list.insert_after(posBefore, 42); PRINT_ELEMENTS(list); } void ForwardListTest::run() { printStart("findBeforeDemo()"); findBeforeDemo(); printEnd("findBeforeDemo()"); }
运行结果:
---------------- findBeforeDemo(): Run Start ----------------
1 42 2 3 4 5 97 98 99
---------------- findBeforeDemo(): Run End ----------------
完整Demo
void ForwardListTest::fullDemo() { // create two forward lists forward_list<int> list1 = { 1, 2, 3, 4 }; forward_list<int> list2 = { 77, 88, 99 }; printLists("initial:", list1, list2); // insert six new element at the beginning of list2 list2.insert_after(list2.before_begin(), 99); list2.push_front(10); list2.insert_after(list2.before_begin(), { 10, 11, 12, 13 }); printLists("6 new elems:", list1, list2); // insert all elements of list2 at the beginning of list1 list1.insert_after(list1.before_begin(), list2.begin(), list2.end()); printLists("list2 into list1:", list1, list2); // delete second element and elements after element with value 99 list2.erase_after(list2.begin()); list2.erase_after(find(list2.begin(), list2.end(), 99), list2.end()); printLists("delete 2nd and after 99:", list1, list2); // sort list1, assign it to list2, and remove duplicates list1.sort(); list2 = list1; list2.unique(); printLists("sorted and unique:", list1, list2); // merge both sorted lists into list1 list1.merge(list2); printLists("merged:", list1, list2); }
运行结果:
---------------- fullDemo(): Run Start ----------------
initial:
list1: 1 2 3 4
list2: 77 88 99
6 new elems:
list1: 1 2 3 4
list2: 10 11 12 13 10 99 77 88 99
list2 into list1:
list1: 10 11 12 13 10 99 77 88 99 1 2 3 4
list2: 10 11 12 13 10 99 77 88 99
delete 2nd and after 99:
list1: 10 11 12 13 10 99 77 88 99 1 2 3 4
list2: 10 12 13 10 99
sorted and unique:
list1: 1 2 3 4 10 10 11 12 13 77 88 99 99
list2: 1 2 3 4 10 11 12 13 77 88 99
merged:
list1: 1 1 2 2 3 3 4 4 10 10 10 11 11 12 12 13 13 77 77 88 88 99 99 99
list2:
---------------- fullDemo(): Run End ----------------
