STL中算法錦集(二)

文章目錄

• STL中算法錦集(二)
• • 一、< algorithm >
  • • 1.std::equal
    • 2.std::equal_range
    • 3.std::fill
    • 4.std::fill_n
    • 5.std::find
    • 6.std::find_end
    • 7.std::find_first_of

一、< algorithm >

1.std::equal

• 原型：

template <class InputIterator1, class InputIterator2>bool equal (InputIterator1 first1, InputIterator1 last1,InputIterator2 first2);template <class InputIterator1, class InputIterator2, class BinaryPredicate>bool equal (InputIterator1 first1, InputIterator1 last1,InputIterator2 first2, BinaryPredicate pred);

• 參數(shù)：

• InputIterator1 first1：第一個區(qū)間的開始
• InputIterator1 last1：第一個區(qū)間的結(jié)束
• InputIterator2 first2：第二個區(qū)間的開始
• BinaryPredicate pred：自定義比較規(guī)則，可以是函數(shù)指針或者仿函數(shù)對象、lambda表達式
• 注意第一個區(qū)間的長度如果比第二個區(qū)間的長度長，那么肯定返回false；
• 反之第一個區(qū)間的長度如果比第二個區(qū)間的長度短，程序正常判斷的

• 作用：[first1,last1)區(qū)間中的每個元素和first2區(qū)間中的對應(yīng)元素是否滿足pred條件
• 返回值：如果第一個區(qū)間中的每個元素和第二個區(qū)間中的對應(yīng)元素都滿足pred條件，返回true，反之返回false
• 實現(xiàn)：

template <class InputIterator1, class InputIterator2>bool equal ( InputIterator1 first1, InputIterator1 last1, InputIterator2 first2 ) {while (first1!=last1) {// or: if (!pred(*first1,*first2))if (!(*first1 == *first2))return false;++first1; ++first2;}return true; }

• 案例：

// equal algorithm example #include <iostream> // std::cout #include <algorithm> // std::equal #include <vector> // std::vectorbool mypredicate (int i, int j) {return (i==j); }int main () {int myints[] = {20,40,60,80,100}; // myints: 20 40 60 80 100std::vector<int>myvector (myints,myints+5); // myvector: 20 40 60 80 100// using default comparison:if ( std::equal (myvector.begin(), myvector.end(), myints) )std::cout << "The contents of both sequences are equal.\n";elsestd::cout << "The contents of both sequences differ.\n";myvector[3]=81; // myvector: 20 40 60 81 100// using predicate comparison:if ( std::equal (myvector.begin(), myvector.end(), myints, mypredicate) )std::cout << "The contents of both sequences are equal.\n";elsestd::cout << "The contents of both sequences differ.\n";return 0; }Output: The contents of both sequences are equal. The contents of both sequence differ.

2.std::equal_range

• 原型：

template <class ForwardIterator, class T>pair<ForwardIterator,ForwardIterator>equal_range (ForwardIterator first, ForwardIterator last, const T& val);template <class ForwardIterator, class T, class Compare>pair<ForwardIterator,ForwardIterator>equal_range (ForwardIterator first, ForwardIterator last, const T& val,Compare comp);

• 參數(shù)：

• ForwardIterator first：區(qū)間的開始
• ForwardIterator last：區(qū)間的結(jié)束
• const T& val：待比較的值
• Compare comp：自定義比較規(guī)則
• 需要排序

• 作用：求[first,last)區(qū)間內(nèi)值為val的范圍，左閉右開區(qū)間
• 返回值：返回值為一個pair的鍵值對，每個元素都是迭代器，[begin,end):代表值為val的開始位置和結(jié)束位置的下一個位置
• 實現(xiàn)：

template <class ForwardIterator, class T>pair<ForwardIterator,ForwardIterator>equal_range (ForwardIterator first, ForwardIterator last, const T& val) {ForwardIterator it = std::lower_bound (first,last,val);return std::make_pair ( it, std::upper_bound(it,last,val) ); }

• 案例：

// equal_range example // equal_range example #include <iostream> // std::cout #include <algorithm> // std::equal_range, std::sort #include <vector> // std::vectorbool mygreater (int i,int j) { return (i>j); }int main () {int myints[] = {10,20,30,30,20,10,10,20};std::vector<int> v(myints,myints+8); // 10 20 30 30 20 10 10 20std::pair<std::vector<int>::iterator,std::vector<int>::iterator> bounds;// using default comparison:std::sort (v.begin(), v.end());// 10 10 10 20 20 20 30 30bounds=std::equal_range (v.begin(), v.end(), 20);// using "mygreater" as comp:std::sort (v.begin(), v.end(), mygreater);// 30 30 20 20 20 10 10 10bounds=std::equal_range (v.begin(), v.end(), 20, mygreater); // std::cout << "bounds at positions " << (bounds.first - v.begin());std::cout << " and " << (bounds.second - v.begin()) << '\n';return 0; }Output: bounds at positions 2 and 5

3.std::fill

• 原型：

template <class ForwardIterator, class T>void fill (ForwardIterator first, ForwardIterator last, const T& val);

• 參數(shù)：

• ForwardIterator first：區(qū)間的開始
• ForwardIterator last：區(qū)間的結(jié)束
• const T& val：填充的val

• 作用：把[first,last)區(qū)間用val值填充
• 返回值：沒有返回值
• 實現(xiàn)：

template <class ForwardIterator, class T>void fill (ForwardIterator first, ForwardIterator last, const T& val) {while (first != last) {*first = val;++first;} }

• 案例：

// fill algorithm example #include <iostream> // std::cout #include <algorithm> // std::fill #include <vector> // std::vectorint main () {std::vector<int> myvector (8);// myvector: 0 0 0 0 0 0 0 0std::fill (myvector.begin(),myvector.begin()+4,5); // myvector: 5 5 5 5 0 0 0 0std::fill (myvector.begin()+3,myvector.end()-2,8); // myvector: 5 5 5 8 8 8 0 0std::cout << "myvector contains:";for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)std::cout << ' ' << *it;std::cout << '\n';return 0; }Output: myvector contains: 5 5 5 8 8 8 0 0

4.std::fill_n

• 原型：

//98 template <class OutputIterator, class Size, class T>void fill_n (OutputIterator first, Size n, const T& val);//11 template <class OutputIterator, class Size, class T>OutputIterator fill_n (OutputIterator first, Size n, const T& val);

• 參數(shù)：

• OutputIterator first：區(qū)間的開始
• Size n
• const T& val

• 作用：從first位置開始填充n個val值
• 返回值：98:沒有返回值。11:返回填充完成后位置的下一個位置
• 實現(xiàn)：

template <class OutputIterator, class Size, class T>OutputIterator fill_n (OutputIterator first, Size n, const T& val) {while (n > 0) {*first = val;++first; --n;}return first; // since C++11 }

• 案例：

// fill_n example #include <iostream> // std::cout #include <algorithm> // std::fill_n #include <vector> // std::vectorint main () {std::vector<int> myvector (8,10); // myvector: 10 10 10 10 10 10 10 10std::fill_n (myvector.begin(),4,20); // myvector: 20 20 20 20 10 10 10 10std::fill_n (myvector.begin()+3,3,33); // myvector: 20 20 20 33 33 33 10 10std::cout << "myvector contains:";for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)std::cout << ' ' << *it;std::cout << '\n';return 0; }Output: myvector contains: 20 20 20 33 33 33 10 10

5.std::find

• 原型：

template <class InputIterator, class T>InputIterator find (InputIterator first, InputIterator last, const T& val);

• 參數(shù)：

• InputIterator first：區(qū)間的開始
• InputIterator last：區(qū)間的結(jié)束
• const T& val：待查找的值val

• 作用：[first,last)區(qū)間內(nèi)查找第一個值為val的元素的位置
• 返回值：返回第一個值為val的元素的位置
• 實現(xiàn)：

template<class InputIterator, class T>InputIterator find (InputIterator first, InputIterator last, const T& val) {while (first!=last) {if (*first==val) return first;++first;}return last; }

• 案例：

// find example #include <iostream> // std::cout #include <algorithm> // std::find #include <vector> // std::vectorint main () {// using std::find with array and pointer:int myints[] = { 10, 20, 30, 40 };int * p;p = std::find (myints, myints+4, 30);if (p != myints+4)std::cout << "Element found in myints: " << *p << '\n';elsestd::cout << "Element not found in myints\n";// using std::find with vector and iterator:std::vector<int> myvector (myints,myints+4);std::vector<int>::iterator it;it = find (myvector.begin(), myvector.end(), 30);if (it != myvector.end())std::cout << "Element found in myvector: " << *it << '\n';elsestd::cout << "Element not found in myvector\n";return 0; }Output: Element found in myints: 30 Element found in myvector: 30

6.std::find_end

• 原型：

template <class ForwardIterator1, class ForwardIterator2>ForwardIterator1 find_end (ForwardIterator1 first1, ForwardIterator1 last1,ForwardIterator2 first2, ForwardIterator2 last2);template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>ForwardIterator1 find_end (ForwardIterator1 first1, ForwardIterator1 last1,ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred);

• 參數(shù)：

• ForwardIterator1 first1：區(qū)間1的開始
• ForwardIterator1 last1：區(qū)間1的結(jié)束
• ForwardIterator2 first2：區(qū)間2的開始
• ForwardIterator2 last2：區(qū)間2的結(jié)束
• BinaryPredicate pred：自定義比較規(guī)則，可以是函數(shù)指針或者仿函數(shù)對象、lambda表達式

• 作用：在[first1,last1)區(qū)間的查找滿足[first2,last2)區(qū)間中的所有元素
• 返回值：如果[first1,last1)區(qū)間查找到[first2,last2)區(qū)間中的所有元素，返回[first2,last2)區(qū)間在[first1,last1)區(qū)間最后一個滿足條件的開始位置
• 實現(xiàn)：

template<class ForwardIterator1, class ForwardIterator2>ForwardIterator1 find_end (ForwardIterator1 first1, ForwardIterator1 last1,ForwardIterator2 first2, ForwardIterator2 last2) {if (first2==last2) return last1; // specified in C++11ForwardIterator1 ret = last1;while (first1 != last1){ForwardIterator1 it1 = first1;ForwardIterator2 it2 = first2;// or: while (pred(*it1,*it2))while (*it1 == *it2) {++it1; ++it2;if (it2==last2) { ret=first1; break; }if (it1==last1) return ret;}++first1;}return ret; }

• 案例：

// find_end example #include <iostream> // std::cout #include <algorithm> // std::find_end #include <vector> // std::vectorbool myfunction (int i, int j) {return (i==j); }int main () {int myints[] = {1,2,3,4,5,1,2,3,4,5};std::vector<int> haystack (myints,myints+10);int needle1[] = {1,2,3};// using default comparison:std::vector<int>::iterator it;it = std::find_end (haystack.begin(), haystack.end(), needle1, needle1+3);if (it!=haystack.end())std::cout << "needle1 last found at position " << (it-haystack.begin()) << '\n';int needle2[] = {4,5,1};// using predicate comparison:it = std::find_end (haystack.begin(), haystack.end(), needle2, needle2+3, myfunction);if (it!=haystack.end())std::cout << "needle2 last found at position " << (it-haystack.begin()) << '\n';return 0; }Output: needle1 found at position 5 needle2 found at position 3

7.std::find_first_of

• 原型：

//98: template <class ForwardIterator1, class ForwardIterator2>ForwardIterator1 find_first_of (ForwardIterator1 first1, ForwardIterator1 last1,ForwardIterator2 first2, ForwardIterator2 last2);template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>ForwardIterator1 find_first_of (ForwardIterator1 first1, ForwardIterator1 last1,ForwardIterator2 first2, ForwardIterator2 last2,BinaryPredicate pred);//11: template <class InputIterator, class ForwardIterator>InputIterator find_first_of (InputIterator first1, InputIterator last1,ForwardIterator first2, ForwardIterator last2);template <class InputIterator, class ForwardIterator, class BinaryPredicate>InputIterator find_first_of (InputIterator first1, InputIterator last1,ForwardIterator first2, ForwardIterator last2,BinaryPredicate pred);

• 參數(shù)：

• InputIterator first1：區(qū)間的開始
• InputIterator last1：區(qū)間的結(jié)束
• ForwardIterator first2：區(qū)間的開始
• ForwardIterator last2：區(qū)間的結(jié)束
• BinaryPredicate pred：自定義比較規(guī)則，可以是函數(shù)指針或者仿函數(shù)對象、lambda表達式

• 作用：在[first1,last1)區(qū)間內(nèi)找[first2,last2)區(qū)間內(nèi)任意一個元素出現(xiàn)的位置
• 返回值：如果在[first1,last1)區(qū)間內(nèi)找[first2,last2)區(qū)間內(nèi)任意一個元素返回該位置的迭代器
• 實現(xiàn)：

template<class InputIterator, class ForwardIterator>InputIterator find_first_of ( InputIterator first1, InputIterator last1,ForwardIterator first2, ForwardIterator last2) {while (first1!=last1) {for (ForwardIterator it=first2; it!=last2; ++it) {// or: if (pred(*it,*first))if (*it==*first1) return first1;}++first1;}return last1; }

• 案例：

// find_first_of example #include <iostream> // std::cout #include <algorithm> // std::find_first_of #include <vector> // std::vector #include <cctype> // std::tolowerbool comp_case_insensitive (char c1, char c2) {return (std::tolower(c1)==std::tolower(c2)); }int main () {int mychars[] = {'a','b','c','A','B','C'};std::vector<char> haystack (mychars,mychars+6);std::vector<char>::iterator it;int needle[] = {'A','B','C'};// using default comparison:it = find_first_of (haystack.begin(), haystack.end(), needle, needle+3);if (it!=haystack.end())std::cout << "The first match is: " << *it << '\n';// using predicate comparison:it = find_first_of (haystack.begin(), haystack.end(),needle, needle+3, comp_case_insensitive);if (it!=haystack.end())std::cout << "The first match is: " << *it << '\n';return 0; }Output: The first match is: A The first match is: a 超強干貨來襲 云風專訪：近40年碼齡，通宵達旦的技術(shù)人生

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