不造轮子之STL中的增删改

程序员的园

发布于 2024-10-09 21:27:51

510

发布于 2024-10-09 21:27:51

文章被收录于专栏：程序员的园——原创文章

在日常的开发中，常涉及到容器的常见操作，如查找、删除、排序等，C++ STL提供了丰富的算法库，可以方便的完成这些操作。为了避免重复造轮子，同时为了提高效率，了解常见的STL算法是非常有必要的。本文将介绍增删改相关算法。

1. std::fill

功能：用指定的值填充范围。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec(5);
   std::fill(vec.begin(), vec.end(), 1);
   for (auto i : vec) {
       std::cout << i << " ";
   }
   std::cout << std::endl;
   return 0;
}

std::fill_n

功能：用指定的值填充范围的前n个元素。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec(5);
   std::fill_n(vec.begin(), 3, 1);
   for (auto i : vec) {
       std::cout << i << " ";
   }
   std::cout << std::endl;
   return 0;
}

2.std::generate

功能：用指定的函数生成值填充范围。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec(5);
   std::generate(vec.begin(), vec.end(), [n = 0]() mutable { return n++; });
   for (auto i : vec) {
       std::cout << i << " "; // 0 1 2 3 4
   }
   std::cout << std::endl;
   return 0;
}

std::generate_n

功能：用指定的函数生成值填充范围的前n个元素。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec(5);
   std::generate_n(vec.begin(), 3, [n = 0]() mutable { return n++; });
   for (auto i : vec) {
       std::cout << i << " "; // 0 1 2
   }
   std::cout << std::endl;
   return 0;
}

3. std::transform

功能：将范围中的元素通过某种规则转换为另一个范围中的元素。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec1{ 1, 2, 3, 4, 5 };
   std::vector<int> vec2(5);
   std::transform(vec1.begin(), vec1.end(), vec2.begin(), [](int i) { return i  2; });
   for (auto i : vec2) {
       std::cout << i << " "; // 2 4 6 8 10
   }
   std::cout << std::endl;
   return 0;
}

4. std::copy

功能：将范围中的元素复制到另一个范围中。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec1{ 1, 2, 3, 4, 5 };
   std::vector<int> vec2(5);//预分配空间
   std::copy(vec1.begin(), vec1.end(), vec2.begin());//vec2为目标范围
   for (auto i : vec2) {
       std::cout << i << " "; // 1 2 3 4 5
   }
   std::cout << std::endl;
   return 0;
}

std::copy_n

功能：将范围中的前n个元素复制到另一个范围中。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec1{ 1, 2, 3, 4, 5 };
   std::vector<int> vec2(5);//预分配空间
   std::copy_n(vec1.begin(), 3, vec2.begin());//vec2为目标范围
   for (auto i : vec2) {
       std::cout << i << " "; // 1 2 3
   }
   std::cout << std::endl;
   return 0;
      
}

std::copy_if

功能：将范围中满足条件的元素复制到另一个范围中。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec1{ 1, 2, 3, 4, 5 };
   std::vector<int> vec2(5);//预分配空间
   std::copy_if(vec1.begin(), vec1.end(), vec2.begin(), [](int i) { return i % 2 == 0; });//vec2为目标范围
   for (auto i : vec2) {
       std::cout << i << " "; // 2 4
   }
   std::cout << std::endl;
   return 0;
}

5. std::remove

功能：删除范围中等于指定值的元素。

include <algorithm>
include <vector>
include <iostream>
int main() {
      
   std::vector<int> vec{ 1, 2, 3, 4, 5 };
   vec.erase(std::remove(vec.begin(), vec.end(), 3), vec.end());
   for (auto i : vec) {
       std::cout << i << " "; // 1 2 4 5
   }
   std::cout << std::endl;
   return 0;
}

std::remove_if

功能：删除范围中满足条件的元素。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec{ 1, 2, 3, 4, 5 };
   vec.erase(std::remove_if(vec.begin(), vec.end(), [](int i) { return i % 2 == 0; }), vec.end());
   for (auto i : vec) {
       std::cout << i << " "; // 1 3 5
   }
   std::cout << std::endl;
   return 0;
}

6. std::replace

功能：将范围中等于指定值的元素替换为另一个值。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec{ 1, 2, 3, 4, 5 };
   std::replace(vec.begin(), vec.end(), 3, 6);
   for (auto i : vec) {
       std::cout << i << " "; // 1 2 6 4 5
   }
   std::cout << std::endl;
   return 0;
}

std::replace_if

功能：将范围中满足条件的元素替换为另一个值。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec{ 1, 2, 3, 4, 5 };  
   std::replace_if(vec.begin(), vec.end(), [](int i) { return i % 2 == 0; }, 6);
   for (auto i : vec) {
       std::cout << i << " "; // 1 6 3 6 5
   }
   std::cout << std::endl;
   return 0;
}

7. std::for_each

功能：对范围中的每个元素执行指定的操作。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec{ 1, 2, 3, 4, 5 };
   std::for_each(vec.begin(), vec.end(), [](int& i) { i = 2; });//对每个元素进行操作
   for (auto i : vec) {
       std::cout << i << " "; // 2 4 6 8 10
   }
   std::cout << std::endl;
   return 0;
}

8. std::reverse

功能：将范围中的元素顺序反转。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec{ 1, 2, 3, 4, 5 };
   std::reverse(vec.begin(), vec.end());
   for (auto i : vec) {
       std::cout << i << " "; // 5 4 3 2 1
   }
   std::cout << std::endl;
   return 0;
}

9. std::swap

功能：交换两个范围中的元素。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec1{ 1, 2, 3, 4, 5 };
   std::vector<int> vec2{ 6, 7, 8, 9, 10 };
   std::swap(vec1, vec2);
   for (auto i : vec1) {
       std::cout << i << " "; // 6 7 8 9 10
   }
   std::cout << std::endl;
   return 0;
}

std::swap_ranges

功能：交换两个范围中的元素。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec1{ 1, 2, 3, 4, 5 };
   std::vector<int> vec2{ 6, 7, 8, 9, 10 };
   std::swap_ranges(vec1.begin(), vec1.end(), vec2.begin());
   for (auto i : vec1) {
       std::cout << i << " "; // 6 7 8 9 10
   }
}

10. std::rotate

功能：将范围中的元素向右旋转指定的步数。

template <class ForwardIterator>
void rotate (ForwardIterator first, ForwardIterator middle, 
  ForwardIterator last);

参数

first：指向序列开始的迭代器。
middle：指向序列中将被旋转到首位的元素的迭代器。
last：指向序列结束的迭代器。

代码示例：

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec{ 1, 2, 3, 4, 5 };
   ///
   std::rotate(vec.begin(), vec.begin() + 2, vec.end());
   for (auto i : vec) {
       std::cout << i << " "; // 3 4 5 1 2
   }
   std::cout << std::endl;
   return 0;
}

11. std::unique

功能：删除范围中连续的重复元素。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec{ 1, 2, 2, 3, 4, 4, 4, 5 };
   vec.erase(std::unique(vec.begin(), vec.end()), vec.end());
   for (auto i : vec) {
       std::cout << i << " "; // 1 2 3 4 5
   }
   std::cout << std::endl;
   return 0;
}

std::unique_copy

功能：将范围中的元素复制到另一个范围，并删除连续的重复元素。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec{ 1, 2, 2, 3, 4, 4, 4, 5 };
   std::vector<int> vec2(vec.size());
   std::unique_copy(vec.begin(), vec.end(), vec2.begin());
   for (auto i : vec2) {
       std::cout << i << " "; // 1 2 3 4 5
   }
   std::cout << std::endl;
   return 0;
}

12. std::clamp

功能：将值限制在指定范围内。小于下限的值将被替换为下限，大于上限的值将被替换为上限。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec{ 1, 2, 3, 4, 5 };
   std::transform(vec.begin(), vec.end(), vec.begin(), [](int i) { return std::clamp(i, 2, 4); });
   for (auto i : vec) {
       std::cout << i << " "; // 2 2 3 4 4
   }
   std::cout << std::endl;
   return 0;
}

13. std::accumulate

功能：计算范围中元素的和。

include <algorithm>
include <vector>
include <iostream>
int main() {
   std::vector<int> vec{ 1, 2, 3, 4, 5 };
   int sum = std::accumulate(vec.begin(), vec.end(), 0);
   std::cout << sum << std::endl; // 15
   return 0;
}

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原始发表：2024-10-01，如有侵权请联系 cloudcommunity@tencent.com 删除

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