迭代器

#include <vector>
#include <iostream>
using namespace std;
void main() {
     vector<int> v; 
    v.push_back(1); v.push_back(2); v.push_back(3); v.push_back(4);
    vector<int>::const_iterator i;    // 常量迭代器
    for(i = v.begin(); i != v.end(); ++i)
        cout << *i << ",";
    cout << endl;
    vector<int>::reverse_iterator r; // 反向迭代器
    for(r = v.rbegin(); r != vrend(); ++r)    // ++r 实际上是往前走
        cout << *r << ",";
    cout << endl;
    vector<int>::iterator j; // 非常量迭代器
    for(j = v.begin(); j != v.end(); ++j)
        *j = 100;
    for(i = v.begin(); i != v.end(); ++i)
        cout << *i << ",";
    cout << endl;
/* 输出：
    1,2,3,4,
    4,3,2,1,
    100,100,100,100,
 */        
}

双向迭代器

随机访问迭代器

不同容器对应迭代器种类

vector的迭代器是随机访问迭代器

算法简介

find()模板

#include <vector>
#include <algorithm>
#include <iostream>
using namespace std;
void main() {
     int array[10] = {10, 20, 30, 40};
    vector<int> v;
    v.push_back(1); v.push_back(2);
    v.push_back(3); v.push_back(4);
    vecotr<int>::iterator p;
    p = find(v.begin(), v.end(), 3);
    if(p != v.end())
        cout << *p << endl; // 输出3 
    p = find(v.begin(), v.end(), 9);
    if(p == v.end())
        cout << "not found" << endl; // 输出 not found
    p = find(v.begin()+1, v.end()-2, 1); //整个容器： [1,2,3,4]， 查找区间： [2,3)
    if(p != v.end())
        cout << *p << endl;    // 输出3
    int *pp = find(array, array+4, 20);
    cout << *pp << endl; // 输出20
}

STL中“大”“小”概念

STL中“相等”概念演示

#include <iostream>
#include <algorithm>
using namespace std;
class A {
      int v;
public:
    A(int n):v(n){}
    bool operator < (const A & a) {
        cout << v << "<" << a.v << "?" << endl;
        return false;
    }
    bool operator == (const A & a) {
         cout << v << "==" << a.v << "?" << endl;
        return v == a.v;       
    }
};
void main() {
     A a[] = {A(1), A(2), A(3), A(4), A(5)};
    cout << binary_search(a, a+4, A(9));
}
/* 输出：
    3<9?
    2<9?
    1<9?
    9<1?
 */