不变序列算法属于C++泛型算法中的一种,不需要修改容器内容。这些算法包括adjacent_find, find, find_end, find_first_of, count, mismatch, equal, for_each, search，下面用程序实例演示每一个算法。
1、find —— 在集合或容器中查找指定元素第一次出现的位置
#include "iostream" //因为语法高亮插件不支持尖括号，故改成引号
#include "algorithm" //实际调试过程中请自行更改
int arr[] = { 11, 22, 33, 44, 55, 66, 77, 88 };
int main ()
{
int *ptr;
ptr = find(arr, arr+8, 33); // 找第一个 33
cout << "First object with value 33 found at offset "
<< (ptr-arr) << endl;
return 0;
}
运行结果:
// First object with value 33 found at offset 2
2、find_end —— 在集合或容器中查找指定子集最后一次出现的位置
#include "iostream"
#include "algorithm"
#include "vector"
using namespace std;
int main ()
{
int ary[] = { 1,2,3,4,5,6,2,3,4,5,6 };
vector v1(ary,ary+11);
vector v2(ary+2,ary+4);
for ( int i = 0; i < v1.size(); i++ )
cout << v1[i] << " "; cout << endl;
for ( int i = 0; i < v2.size(); i++ )
cout << v2[i] << " "; cout << endl;
vector::iterator pos;
pos = find_end(v1.begin(),v1.end(), // 范围(集合)
v2.begin(),v2.end()); // 子区间(子集)
cout << "Position of last subrange of subrange "
<< "(2,4) found starting with element "
<< distance(v1.begin(),pos) + 1
<< endl;
return 0;
}
运行结果:
// 1 2 3 4 5 6 2 3 4 5 6
// 3 4
// Position of last subrange of subrange (2,4)
// found starting with element 8
3、find_first_of —— 在集合或容器中查找指定子集第一次出现的位置
#include "iostream"
#include "vector"
#include "list"
#include "algorithm"
using namespace std;
int main()
{
vector V;
list searchV;
for ( int i = 1; i < 11; i++ )
{
V.insert(V.end(),i % 5); //i对5取余后从容器尾部入队
}
for ( int i = 2; i < 5; i++ )
{
searchV.insert(searchV.end(),i);
}
copy(V.begin(),V.end(),
ostream_iterator(cout," ")); //从头到尾地复制到输出端
cout << endl;
copy(searchV.begin(),searchV.end(),
ostream_iterator(cout," "));
cout << endl;
// 搜索第一次匹配searchV的首元素位置
vector::iterator pos; //迭代器
pos = find_first_of (V.begin(), V.end(),// 范围(集合)
searchV.begin(), // 搜索子集头
searchV.end()); // 搜索子集尾
cout << "first element of searchV in V is element "
<< distance(V.begin(),pos) + 1
<< endl;
// 搜索最后一次匹配searchV的末元素位置
vector::reverse_iterator rpos; //反向迭代器
rpos = find_first_of (V.rbegin(), V.rend(), // 范围(集合)
searchV.begin(), // 搜索子集头
searchV.end()); // 搜索子集尾
cout << "last element of searchV in V is element "
<< distance(V.begin(),rpos.base())
<< endl;
return 0;
}
运行结果:
// 1 2 3 4 0 1 2 3 4 0
// 2 3 4
// first element of searchV in V is element 2
// last element of searchV in V is element 9
4、find_if —— 从集合或容器中依次取元素作为指定函数的参数，如果指定函数返回真则返回当前元素位置
#include "iostream"
#include "algorithm"
#include "string"
using namespace std;
//------------------------------------------------------
bool isDon (string name) // 如果name等于Don则返回真
{
return name == "Don";
}
//------------------------------------------------------
string names[] = { "George", "Estelle", "Don", "Mike" };
int main ()
{
string* ptr;
ptr = find_if (names, names+4, isDon);
if (ptr == names+4)
cout << "Don is not on the list.\n";
else
cout << "Don is element "
<< (ptr - names)
<< " on the list.\n";
return 0;
}
运行结果:
// Don is element 2 on the list.
5、adjacent_find —— 在集合或者容器中查找值相等的相邻元素，如果找到则返回第一个元素位置
#include "algorithm"
#include "iostream"
using namespace std;
void main()
{
const int ARRAY_SIZE = 8 ;
int IntArray[ARRAY_SIZE] = { 1, 2, 3, 4, 4, 5, 6, 7 } ;
int *location;//存储第一对匹配的连续元素地址
// 打印 IntArray 内容
cout << "IntArray { " ;
for(int i = 0; i < ARRAY_SIZE; i++)
cout << IntArray[i] << ", " ;
cout << " }" << endl ;
// 在区间[first, last + 1)中查找第一对匹配的连续元素
// in the range [first, last + 1)
// 此版本使用运算符==进行匹配
location = adjacent_find(IntArray, IntArray +
ARRAY_SIZE);
//如果找到匹配元素则打印出来
if (location != IntArray + ARRAY_SIZE)// 如果匹配
// 连续元素被找到
cout << "Found adjacent pair of matching "
<< "elements: ("
<< *location << ", " << *(location + 1) << "), "
<< "at location " << location - IntArray << endl;
else // 连续元素未找到
cout << "No adjacent pair of matching elements were"
<< " found" << endl; cout << endl; cout << endl;
}
运行结果:
// IntArray { 1, 2, 3, 4, 4, 5, 6, 7, }
// Found adjacent pair of matching elements:
// (4, 4), at location 3
6、count —— 在集合或者容器中查找指定内容，返回指定内容的个数
#include "isotream"
#include "algorithm"
using namespace std;
int main ()
{
int a[] = {2,4,5,7,3,2,4,8,2};
int N = 0;
N = count (a, a + (sizeof(a) / sizeof(a[0])), //查找的起始地址
2); // 要查找的内容
cout << "Array consists " << N << " 2's" << endl;
return 0;
}
运行结果:
// Array consists 3 2's
7、count_if —— 从集合或容器中依次取元素作为指定函数的参数，如果指定函数返回真则返回匹配元素的个数
#include "iostream"
#include "algorithm"
#include "functional"
#include "string"
#include "vector"
using namespace std;
//如果参数str第一个字母为s则返回真
int MatchFirstChar( const string& str)
{
string s("S") ;
return s == str.substr(0,1) ;
}
//---------------------------------------------------
void main()
{
const int VECTOR_SIZE = 8 ;
// 定义一个string vector 容器模板
typedef vector StrVector ;
// 为 string verctor 容器定义一个迭代器模板
typedef StrVector::iterator StrVectIt ;
StrVector NamesV(VECTOR_SIZE);
//定义一个StrVector容器
StrVectIt start, end, it ;
int result = 0 ; // 存储匹配的元素个数
// 初始化 NamesV 容器
NamesV[0] = "She" ;
NamesV[1] = "Sells" ;
NamesV[2] = "Sea" ;
NamesV[3] = "Shells" ;
NamesV[4] = "by" ;
NamesV[5] = "the" ;
NamesV[6] = "Sea" ;
NamesV[7] = "Shore" ;
start = NamesV.begin() ; //NamesV 容器的第一个元素
end = NamesV.end() ; //NamesV 容器的最后一个元素
//打印 NamesV 容器的所有元素
cout << "NamesV { " ;
for(it = start; it != end; it++)
cout << *it << " " ;
cout << " }\n" << endl ;
//计算区间 [first, last +1)里面首字母以s开头的元素个数
result = count_if(start, end, MatchFirstChar);
// 打印字母以s开头的元素个数
cout << "Number of elements that start"
<< " with letter \"S\" = "
<< result << endl ;
}
运行结果:
// NamesVect { She Sells Sea Shells by the Sea Shore }
// Number of elements that start with letter "S" = 6
8、mismatch —— 比较两个集合或者容器的内容，返回第一对不匹配的元素指针
#include "iostream"
#include "algorithm"
using namespace std;
int main ()
{
int A1[] = { 3, 1, 4, 1, 5, 9, 3 };
int A2[] = { 3, 1, 4, 2, 8, 5, 7 };
const int N = sizeof(A1) / sizeof(int);
//由于插件不支持尖括号，请自行将pair后面的【】换成尖括号
pair【int*, int*】 result =
mismatch(A1, A1 + N, A2);
cout << "The first mismatch is in position "
<< result.first - A1 + 1 << endl;
cout << "Values are: " << *(result.first)
<< ", " << *(result.second) << endl;
return 0;
}
运行结果:
// The first mismatch is in position 4
// Values are: 1, 2
9、for_each —— 将集合或者容器内指定范围的元素作为参数传入指定函数执行
#include "iostream"
#include "algorithm"
using namespace std;
void inch_to_cm (double in)
{
cout << ( in * 2.54 ) << ' ';
}
//-------------------------------------------------------
int main ()
{
// 一组以厘米为单位的数据值
double inches[] = { 3.5, 6.2, 1.0, 12.87, 4.35 };
// 按英寸为单位转换输出
for_each (inches, inches+5, inch_to_cm);
cout << endl;
return 0;
}
运行结果:
// 8.89 15.748 2.54 32.6898 11.049
10、for_each —— 在集合或者容器中查找另一集合或者容器，如果找到则返回匹配的位置指针，否则返回第一个的尾指针
#include "iostream"
#include "algorithm"
using namespace std;
int source[] = { 11, 44, 33, 11, 22, 33, 11, 22, 44 };
int pattern[] = { 11, 22, 33 };
int main ()
{
int* ptr;
ptr = search (source, source+9, pattern, pattern+3);
if (ptr == source+9) // if past-the- end
cout << "No match found\n";
else
cout << "Match at " << (ptr - source) << endl;
return 0;
}
OUTPUT:
// Match at 3
除非注明，文章均为CppLive 编程在线原创，转载请注明出处，谢谢。
