什么是成对向量？ A. 一对 存储两个相互映射的值的容器，以及 矢量 包含多个这样的对的向量称为对向量。
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// C++ program to demonstrate vector of pairs #include<bits/stdc++.h> using namespace std; int main() { //declaring vector of pairs vector< pair < int , int > > vect; // initialising 1st and 2nd element of // pairs with array values int arr[] = {10, 20, 5, 40 }; int arr1[] = {30, 60, 20, 50}; int n = sizeof (arr)/ sizeof (arr[0]); // Entering values in vector of pairs for ( int i=0; i<n; i++) vect.push_back( make_pair(arr[i],arr1[i]) ); // Printing the vector for ( int i=0; i<n; i++) { // "first" and "second" are used to access // 1st and 2nd element of pair respectively cout << vect[i].first << " " << vect[i].second << endl; } return 0; } |
输出：
10 30 20 60 5 20 40 50
案例1：根据成对的第一个元素按升序排序向量元素。 这种类型的排序可以使用简单的“sort（）”函数实现。默认情况下，sort函数根据成对的第一个元素对向量元素进行排序。
// C++ program to demonstrate sorting in // vector of pair according to 1st element // of pair #include<bits/stdc++.h> using namespace std; int main() { // Declaring vector of pairs vector< pair < int , int > > vect; // Initializing 1st and 2nd element of // pairs with array values int arr[] = {10, 20, 5, 40 }; int arr1[] = {30, 60, 20, 50}; int n = sizeof (arr)/ sizeof (arr[0]); // Entering values in vector of pairs for ( int i=0; i<n; i++) vect.push_back( make_pair(arr[i],arr1[i]) ); // Printing the original vector(before sort()) cout << "The vector before sort operation is:" ; for ( int i=0; i<n; i++) { // "first" and "second" are used to access // 1st and 2nd element of pair respectively cout << vect[i].first << " " << vect[i].second << endl; } // Using simple sort() function to sort sort(vect.begin(), vect.end()); // Printing the sorted vector(after using sort()) cout << "The vector after sort operation is:" ; for ( int i=0; i<n; i++) { // "first" and "second" are used to access // 1st and 2nd element of pair respectively cout << vect[i].first << " " << vect[i].second << endl; } return 0; } |
输出：
The vector before applying sort operation is: 10 30 20 60 5 20 40 50 The vector after applying sort operation is: 5 20 10 30 20 60 40 50
案例2：根据成对的第二个元素按升序排序向量元素。 有些情况下，我们需要根据向量对的第二个元素对向量的元素进行排序。为此，我们修改sort（）函数，并传递第三个参数，即对sort（）函数中用户定义的显式函数的调用。
// C++ program to demonstrate sorting in vector // of pair according to 2nd element of pair #include<bits/stdc++.h> using namespace std; // Driver function to sort the vector elements // by second element of pairs bool sortbysec( const pair< int , int > &a, const pair< int , int > &b) { return (a.second < b.second); } int main() { // declaring vector of pairs vector< pair < int , int > > vect; // Initialising 1st and 2nd element of pairs // with array values int arr[] = {10, 20, 5, 40 }; int arr1[] = {30, 60, 20, 50}; int n = sizeof (arr)/ sizeof (arr[0]); // Entering values in vector of pairs for ( int i=0; i<n; i++) vect.push_back( make_pair(arr[i],arr1[i]) ); // Printing the original vector(before sort()) cout << "The vector before sort operation is:" ; for ( int i=0; i<n; i++) { // "first" and "second" are used to access // 1st and 2nd element of pair respectively cout << vect[i].first << " " << vect[i].second << endl; } // Using sort() function to sort by 2nd element // of pair sort(vect.begin(), vect.end(), sortbysec); // Printing the sorted vector(after using sort()) cout << "The vector after sort operation is:" ; for ( int i=0; i<n; i++) { // "first" and "second" are used to access // 1st and 2nd element of pair respectively cout << vect[i].first << " " << vect[i].second << endl; } return 0; } |
输出：
The vector before applying sort operation is: 10 30 20 60 5 20 40 50 The vector after applying sort operation is: 5 20 10 30 40 50 20 60
C++集2中对的排序向量 （按第一和第二降序排序） 本文由 曼吉星 .如果你喜欢GeekSforgek，并想贡献自己的力量，你也可以使用 写极客。组织 或者把你的文章寄去评论-team@geeksforgeeks.org.看到你的文章出现在Geeksforgeks主页上，并帮助其他极客。
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