search
HomeBackend DevelopmentC++## Are Iterators to Erased Elements in a `std::vector` Still Valid?

## Are Iterators to Erased Elements in a `std::vector` Still Valid?

std::vector Iterator Invalidation: Unearthing the Validity of Iterators After Erasure

In the realm of C , the intricacies of vector iterators and their behavior after erasures can be a source of confusion. To delve into this issue, we'll explore a specific scenario:

Validating Iterator Persistence After an Erase Operation

Pertinent questions arise regarding the validity of an iterator pointing directly to the erased element in a std::vector. The prevailing notion is that iterators pointing to positions after the erased element are invalidated. However, the question remains: is the iterator pointing to the exact location of the erased element still valid?

Analysis and Example

To shed light on this issue, consider the following code snippet, which attempts to eliminate all odd integers from a vector:

<code class="cpp">vector<int> vec;

for (int i = 0; i ::iterator it = vec.begin();
while (it != vec.end()) {
    if (*it % 2 == 1) vec.erase(it);
    else ++it;
}</int></code>

While this code may appear to function correctly, it's crucial to delve deeper to determine its validity.

Answering the Question

The answer unequivocally points to the invalidation of not only iterators pointing to positions after the erased element but also the iterator pointing to the exact location of that element.

However, erasing an element provides a returned iterator pointing immediately after the removed element(s) or to the end if there are none remaining. This allows for seamless continuation of iteration.

Efficient Elimination of Odd Elements

It's worth noting that the code snippet presented is not the most efficient method for removing odd elements. A significantly more efficient approach involves the erase-remove idiom, which utilizes a custom predicate to locate and identify elements for removal. For example, we can define a predicate called is_odd and use it with remove_if and erase:

<code class="cpp">bool is_odd(int x) { return (x % 2) == 1; }
vec.erase(remove_if(vec.begin(), vec.end(), is_odd), vec.end());</code>

This eliminates the costly movement of elements, reducing the time complexity to O(n).

The above is the detailed content of ## Are Iterators to Erased Elements in a `std::vector` Still Valid?. For more information, please follow other related articles on the PHP Chinese website!

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
C  : Is It Dying or Simply Evolving?C : Is It Dying or Simply Evolving?Apr 24, 2025 am 12:13 AM

C isnotdying;it'sevolving.1)C remainsrelevantduetoitsversatilityandefficiencyinperformance-criticalapplications.2)Thelanguageiscontinuouslyupdated,withC 20introducingfeatureslikemodulesandcoroutinestoimproveusabilityandperformance.3)Despitechallen

C   in the Modern World: Applications and IndustriesC in the Modern World: Applications and IndustriesApr 23, 2025 am 12:10 AM

C is widely used and important in the modern world. 1) In game development, C is widely used for its high performance and polymorphism, such as UnrealEngine and Unity. 2) In financial trading systems, C's low latency and high throughput make it the first choice, suitable for high-frequency trading and real-time data analysis.

C   XML Libraries: Comparing and Contrasting OptionsC XML Libraries: Comparing and Contrasting OptionsApr 22, 2025 am 12:05 AM

There are four commonly used XML libraries in C: TinyXML-2, PugiXML, Xerces-C, and RapidXML. 1.TinyXML-2 is suitable for environments with limited resources, lightweight but limited functions. 2. PugiXML is fast and supports XPath query, suitable for complex XML structures. 3.Xerces-C is powerful, supports DOM and SAX resolution, and is suitable for complex processing. 4. RapidXML focuses on performance and parses extremely fast, but does not support XPath queries.

C   and XML: Exploring the Relationship and SupportC and XML: Exploring the Relationship and SupportApr 21, 2025 am 12:02 AM

C interacts with XML through third-party libraries (such as TinyXML, Pugixml, Xerces-C). 1) Use the library to parse XML files and convert them into C-processable data structures. 2) When generating XML, convert the C data structure to XML format. 3) In practical applications, XML is often used for configuration files and data exchange to improve development efficiency.

C# vs. C  : Understanding the Key Differences and SimilaritiesC# vs. C : Understanding the Key Differences and SimilaritiesApr 20, 2025 am 12:03 AM

The main differences between C# and C are syntax, performance and application scenarios. 1) The C# syntax is more concise, supports garbage collection, and is suitable for .NET framework development. 2) C has higher performance and requires manual memory management, which is often used in system programming and game development.

C# vs. C  : History, Evolution, and Future ProspectsC# vs. C : History, Evolution, and Future ProspectsApr 19, 2025 am 12:07 AM

The history and evolution of C# and C are unique, and the future prospects are also different. 1.C was invented by BjarneStroustrup in 1983 to introduce object-oriented programming into the C language. Its evolution process includes multiple standardizations, such as C 11 introducing auto keywords and lambda expressions, C 20 introducing concepts and coroutines, and will focus on performance and system-level programming in the future. 2.C# was released by Microsoft in 2000. Combining the advantages of C and Java, its evolution focuses on simplicity and productivity. For example, C#2.0 introduced generics and C#5.0 introduced asynchronous programming, which will focus on developers' productivity and cloud computing in the future.

C# vs. C  : Learning Curves and Developer ExperienceC# vs. C : Learning Curves and Developer ExperienceApr 18, 2025 am 12:13 AM

There are significant differences in the learning curves of C# and C and developer experience. 1) The learning curve of C# is relatively flat and is suitable for rapid development and enterprise-level applications. 2) The learning curve of C is steep and is suitable for high-performance and low-level control scenarios.

C# vs. C  : Object-Oriented Programming and FeaturesC# vs. C : Object-Oriented Programming and FeaturesApr 17, 2025 am 12:02 AM

There are significant differences in how C# and C implement and features in object-oriented programming (OOP). 1) The class definition and syntax of C# are more concise and support advanced features such as LINQ. 2) C provides finer granular control, suitable for system programming and high performance needs. Both have their own advantages, and the choice should be based on the specific application scenario.

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

VSCode Windows 64-bit Download

VSCode Windows 64-bit Download

A free and powerful IDE editor launched by Microsoft

Atom editor mac version download

Atom editor mac version download

The most popular open source editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Dreamweaver Mac version

Dreamweaver Mac version

Visual web development tools

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment