STLalgorithm算法count(10)
原文地址:http://www.cplusplus.com/reference/algorithm/count/
function template
std::count
template <class InputIterator, class T>
typename iterator_traits
count (InputIterator first, InputIterator last, const T& val);
Count appearances of value in range
Returns the number of elements in the range [first,last)
that compare equal to val.
返回first,last之间和元素val相等的元素的个数。
例子:
#include
#include
#include
#include
using namespace std;
void count1(){
vector
array<int,7> ai{888,666,555,222,111,555,777};
cout<<”vi=”;
for(int &i:vi)
cout<<i<<” “;
cout<<endl;
int cv=count(vi.begin(),vi.end(),9);
cout<<"9 在vi中出现了"<<cv<<"次"<<endl;
cout<<"ai=";
for(int &i:ai)
cout<<i<<" ";
cout<<endl;
int ca=count(ai.begin(),ai.end(),555);
cout<<"555 在ai中出现了"<<ca<<"次"<<endl;
}
运行结果:
The function uses operator==
to compare the individual elements to val.
该函数使用operator==来比较各个元素和val是否相等。
The behavior of this function template is equivalent to:
1 | 1 |
1 | template <class InputIterator, class T> |
Parameters
first, last
Input iterators to the initial and final positions of the sequence of elements. The range used is [first,last)
, which contains all the elements between first and last, including the element pointed by first but not the element pointed by last.
比较的范围。
val
Value to match.
T shall be a type supporting comparisons with the elements pointed by InputIterator using operator==
(with the elements as left-hand side operands, and val as right-hand side).
要比较的值。
Return value
The number of elements in the range [first,last)
that compare equal to val.
The return type (iterator_traits
匹配的元素的个数。
Example
1 | 1 |
1 | // count algorithm example |
Output:
10 appears 3 times.
20 appears 3 times.
Complexity
Linear in the distance between first and last: Compares once each element.
Data races
The objects in the range [first,last)
are accessed (each object is accessed exactly once).
Exceptions
Throws if either an element comparison or an operation on an iterator throws.
Note that invalid arguments cause undefined behavior.
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转载请注明出处:http://blog.csdn.net/qq844352155
author:天下无双
Email:coderguang@gmail.com
2014-9-11
于GDUT
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- 本文作者: royalchen
- 本文链接: http://www.royalchen.com/2016/02/24/stlalgorithm算法count10/
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