map

map是一种映射类型,看网上的说法是红黑树实现的,而且还是有序的

赋值和访问

#include <iostream>
#include <map>

using namespace std;

int main() {
    map<int, string> a;
    a[0] = "hello";
    a[1] = "world";
    cout << a[0];
    return 0;
}

遍历

遍历值的方法

#include <iostream>
#include <map>

using namespace std;

int main() {
    map<int, string> a;
    a[0] = "hello";
    a[1] = "world";
    for (auto &p : a) {
        cout << p.second << " ";
    }
    return 0;
}

遍历key的方法

#include <iostream>
#include <map>

using namespace std;

int main() {
    map<int, string> a;
    a[0] = "hello";
    a[1] = "world";
    for (auto &p : a) {
        cout << p.first << " ";
    }
    return 0;
}

通过迭代器访问元素

#include <map>
#include <iostream>

using namespace std;

int main() {
    map<int, string> a;
    a[0] = "hello";
    a[1] = "world";
    auto it = a.begin();
    cout << it->first;
    return 0;
}

通过迭代器遍历

#include <map>
#include <iostream>

using namespace std;

int main() {
    map<int, string> a;
    a[0] = "hello";
    a[1] = "world";

    for(auto it = a.begin(); it != a.end(); it++) {
        cout << it->first;
    }
    return 0;
}

删除数据

通过erase()函数删除,删除某一个元素之前首先需要得到这个元素的迭代器

#include <map>
#include <iostream>

using namespace std;

int main() {
    map<int, string> a;
    a[0] = "hello";
    a[1] = "world";
    auto it = a.begin();
    a.erase(it);

    for(auto it = a.begin(); it != a.end(); it++) {
        cout << it->first;
    }
    return 0;
}

通过insert()函数插入数据

插入到某个位置是无意义的,因为map是有序的

#include <map>
#include <iostream>

using namespace std;

int main() {
    map<int, string> a;
    a[0] = "hello";
    a[1] = "world";
    auto it = a.begin();
    a.erase(it);
    a.insert(pair<int,string>(10,"h"));
    for(auto it = a.begin(); it != a.end(); it++) {
        cout << it->first<<" ";
    }
    return 0;
}
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