C/C++ STL

Resources

• Hacking CPP https://hackingcpp.com/
• Programiz https://www.programiz.com/cpp-programming/online-compiler/
• CppReference https://en.cppreference.com/w/

Algorithm

sort

bool cmp(const vector<int>& a, const vector<int>& b) {
    return a[0] == b[0]? a[1] < b[1]: a[0] < b[0];
}
vector<vector<int>> arrs;
sort(arrs.begin(), arrs.end(), cmp);
sort(arrs.begin(), arrs.end(), [](const vector<int>& a, const vector<int>& b) {
  return COST(a) < COST(b);
});

next_permutation

string s = "2231";

• return {bool}, 表示是否还有下一个增序 (或者自定义 cmp) 排列结果.

while (next_permutation(s.begin(), s.end())) {
    cout << "-" << s;
}

• output

-2312-2321-3122-3212-3221

• next_permutation 具体实现 https://leetcode-cn.com/problems/next-permutation/

Container

STL 容器常用操作: 创建, 遍历, 增删查改, ...

basic

• assignment: 创建, 赋值

• iteration: 迭代

• insert / erase: 值, 添加 / 删除

• interact with C: 与 C 风格指针函数交互

size & capacity

size, 当前容器实际包含的元素个数

• size() → number of elements in vector
• resize(new_number_of_elements)
• assign(size, value)→ 直接分配元素个数

capacity, 当前容器总容量, 预留空间大小

• capacity() → number of available memory slots
• reserve(new_capacity)

iteration

• common

// range based loop
for (auto i : items);  // 'i' is a reference to an item of items
for (auto &i : items); // 'i' is copied from an item of items
for (auto const &i : items); // const & avoid making copies
// iterators
for (auto i = begin(items); i != end(items); ++i) { cout << *i << endl; };
for (auto i = rbegin(items); i != rend(items); ++i) { cout << *i << endl; };  // reverse
for (auto i = cbegin(items); i != cend(items); ++i) { cout << *i << endl; };  // const

• vector

vector<int> items;
for (int i = 0; i < items.size(); i++) cout << items[i] << endl;

• map

map<int, int> mappers;
for (auto m : mappers) cout << m.first << ' ' << m.second << endl;

assignment

• assign

vector<int> v;
v.assign(size);
v.assign(size, value);

• constructor

vector<int> v2(v.begin(), v.end());

vector<int> vec1 {10, 20, 30};
vector<int> vec2 = {10, 20, 30};	// c++[11, 14, 17, ...]

static const int arr[] = {16,2,77,29};
vector<int> vec3(arr, arr + sizeof(arr)/sizeof(arr[0]));

String

Number <=> String

Number to String

int number = 123456;
string x = to_string(number);

cout << to_string(123.456) << endl; // 123.456
cout << to_string(1234567) << endl; // 1234567
cout << to_string(1e5+2) << endl;   // 100002.000000

String to Number (C++11)

• https://en.cppreference.com/w/cpp/string/basic_string/stol

stoi(); stol(); stoll();
stoul(); stoull();
stof(); stod(); stold();

• stoi(str) example

std::string str1 = "45";                // 45
std::string str2 = "3.14159";           // 3
std::string str3 = "31337 with words";  // 31337

References

• https://en.cppreference.com/w/
• https://hackingcpp.com/
• https://www.programiz.com/cpp-programming/library-function