为什么 vector::erase 似乎会导致崩溃?
Why does vector::erase seem to cause a crash?
当删除 first1.erase(std::next(first1.begin(), i));
时,会进行第二个循环,这有点奇怪,因为 first2.erase(first2.begin() + 4, first2.end());
工作正常
#include <iostream>
#include <vector>
int main ()
{
std::vector<int> first1 = {0,1,2,3,4,5};
std::vector<int> first2 = {0,1,2,3,4,5};
std::vector<int> second;
std::vector<int> third;
for(size_t i = 4; i < first1.size(); ++i){
auto child = first1[i];
second.push_back(child);
first1.erase(std::next(first1.begin(), i));
}
third.assign(first2.begin() + 4, first2.end());
first2.erase(first2.begin() + 4, first2.end());
std::cout << "Size of first: " << int (first1.size()) << '\n';
std::cout << "Size of second: " << int (second.size()) << '\n';
std::cout << "Size of first: " << int (first2.size()) << '\n';
std::cout << "Size of third: " << int (third.size()) << '\n';
return 0;
}
输出:
Size of first1: 5
Size of second: 1
Size of first2: 4
Size of third: 2
我预计 first1/second
与 first2/third
相同
你可以在这里测试http://cpp.sh/9ltkw
循环第一次迭代后
for(size_t i = 4; i < first1.size(); ++i){
auto child = first1[i];
second.push_back(child);
first1.erase(std::next(first1.begin(), i));
}
i
将等于 5
而 first1.size() 也将等于 5。因此只有向量的一个元素被删除。
您可以像这样重写循环
for(size_t i = 4; i != first1.size(); ){
auto child = first1[i];
second.push_back(child);
first1.erase(std::next(first1.begin(), i));
}
得到预期的结果。
在这些陈述中
third.assign(first2.begin() + 4, first2.end());
first2.erase(first2.begin() + 4, first2.end());
有2个元素被赋值和擦除。
当删除 first1.erase(std::next(first1.begin(), i));
时,会进行第二个循环,这有点奇怪,因为 first2.erase(first2.begin() + 4, first2.end());
工作正常
#include <iostream>
#include <vector>
int main ()
{
std::vector<int> first1 = {0,1,2,3,4,5};
std::vector<int> first2 = {0,1,2,3,4,5};
std::vector<int> second;
std::vector<int> third;
for(size_t i = 4; i < first1.size(); ++i){
auto child = first1[i];
second.push_back(child);
first1.erase(std::next(first1.begin(), i));
}
third.assign(first2.begin() + 4, first2.end());
first2.erase(first2.begin() + 4, first2.end());
std::cout << "Size of first: " << int (first1.size()) << '\n';
std::cout << "Size of second: " << int (second.size()) << '\n';
std::cout << "Size of first: " << int (first2.size()) << '\n';
std::cout << "Size of third: " << int (third.size()) << '\n';
return 0;
}
输出:
Size of first1: 5
Size of second: 1
Size of first2: 4
Size of third: 2
我预计 first1/second
与 first2/third
你可以在这里测试http://cpp.sh/9ltkw
循环第一次迭代后
for(size_t i = 4; i < first1.size(); ++i){
auto child = first1[i];
second.push_back(child);
first1.erase(std::next(first1.begin(), i));
}
i
将等于 5
而 first1.size() 也将等于 5。因此只有向量的一个元素被删除。
您可以像这样重写循环
for(size_t i = 4; i != first1.size(); ){
auto child = first1[i];
second.push_back(child);
first1.erase(std::next(first1.begin(), i));
}
得到预期的结果。
在这些陈述中
third.assign(first2.begin() + 4, first2.end());
first2.erase(first2.begin() + 4, first2.end());
有2个元素被赋值和擦除。