问题描述
我想要做的是在下面的代码中注释。
作为find给出一个指向找到的第一个值的迭代器..我想达到我想要的给定向量中的最后一个值选择使用查找功能。
谢谢。
what i want to do is commented in the code below.
as find gives an iterator pointing to the first value found.. i want to reach the last value in my given vector of my desired choice using find function.
Thanks.
vector<int>a = {5,1,2,3,5,4,5,6 };
//i want to make my iterator iter point to the second last "5" in the given vector i.e a[6].
auto iter = a.begin();
do {
auto ptr = find(iter, a.end(), 5);
iter = ptr + 1;
} while (iter != a.end());
// error shown is vector iterator + offset out of range and the program crashes
我的尝试：
i havent尝试了什么特别的但也许迭代器的添加肯定会有一些问题。
一个可能的解决方案是或者iter = ptr + 1;使用iter = iter + 1;
但这可能会增加时间复杂度，这不是我问题的完美解决方案。
What I have tried:
i havent tried anything special. but maybe there must be some problems with the iterators addition.
one possible solution is instead or iter=ptr+1; use iter=iter+1;
but this may increase the time complexity and this is not the perfect solution to my question.
推荐答案
auto iter = find( a.rbegin(), a.rend(), 5);？
试试
?
Try
#include <algorithm>
#include <vector>
#include <iostream>
using namespace std;
int main()
{
vector<int>a = {5,1,2,3,5,4,5,6 };
auto iter = find( a.rbegin(), a.rend(), 5);
if ( (iter != a.rend())) std::cout << "found at position " << (a.rend() - iter- 1 ) << endl;
}
iter++;//incrementing the iterator
看看是如何做到的并起诉调试器。
提示：阅读一些文档并搜索示例代码; - ）
Take a look how cplpusplus is doing it and sue a debugger.
Tip: Read some documentation and search for example code ;-)
auto iter = a.begin();
while (true) {
auto ptr = find(iter, a.end(), 5);
if (ptr == a.end())
break; // not found, so break out and leave iter on the last found value
iter = ptr + 1;
}
这篇关于使用find（）到达向量中我们选择的最后一个元素的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！