STL algorithm算法find（16）

原文地址：http://www.cplusplus.com/reference/algorithm/find/

function template

<algorithm>

std::find

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

Find value in range

Returns an iterator to the first element in the range[first,last)that compares equal toval. If no such element is found, the function returnslast.

返回范围内与val相等的第一个元素的迭代器，如果没有这样的元素，那么将返回last.

例子：

#include <iostream>
#include <algorithm>
#include <vector>
#include <array>
using namespace std;

void find2(){
    vector<int> vi{1,5,7,8,9,9,8,5,9};
    cout<<"vi=";
    for(int &i:vi)
        cout<<i<<" ";
    cout<<endl;

    auto it=find(vi.begin(),vi.end(),8);
    cout<<"auto it=find(vi.begin(),vi.end(),8);"<<endl;
    cout<<"(it-1)="<<*(it-1)<<endl;
    cout<<"it="<<*it<<endl;
    cout<<"(it+1)="<<*(it+1)<<endl;

    auto it2=find(vi.begin(),vi.end(),18);
    cout<<"auto it2=find(vi.begin(),vi.end(),18);"<<endl;
    cout<<"(it2-1)="<<*(it2-1)<<endl;
    cout<<"it2="<<*it2<<endl;
    cout<<"(it2+1)="<<*(it2+1)<<endl;
    if(it2==vi.end())
        cout<<"it2==vi.end()"<<endl;


}

运行截图：

The function usesoperator==to compare the individual elements toval.

使用operator==来比较元素与val是否相等。

The behavior of this function template is equivalent to:

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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; }

Parameters

first, last

Input iteratorsto the initial and final positions in a sequence. The range searched is[first,last), which contains all the elements betweenfirstandlast, including the element pointed byfirstbut not the element pointed bylast.
比较的范围。

val

Value to search for in the range.
Tshall be a type supporting comparisons with the elements pointed byInputIteratorusingoperator==(with the elements as left-hand side operands, andvalas right-hand side).

比较的值。

Return value

An iterator to the first element in the range that compares equal toval.
If no elements match, the function returnslast.

返回范围内与val相等的第一个元素的迭代器，如果没有这样的元素，那么将返回last.

Example

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// find example #include <iostream> // std::cout #include <algorithm> // std::find #include <vector> // std::vector int 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'; else std::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'; else std::cout << "Element not found in myints\n"; return 0; }

Edit & Run

Output:

Element found in myints: 30
Element found in myvector: 30

Complexity

Up to linear in thedistancebetweenfirstandlast: Compares elements until a match is found.

Data races

Some (or all) of the objects in the range[first,last)are accessed (once at most).

Exceptions

Throws if either an element comparison or an operation on an iterator throws.
Note that invalid arguments causeundefined behavior.

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转载请注明出处：http://blog.csdn.net/qq844352155

author:天下无双

Email:[e-mail]

2014-9-11

于GDUT

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