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priority_queue custom type, the processing method of the comparison function
#include <bits/stdc++.h>
using namespace std;
struct Node{
int val;
int cnt;
Node(int a, int b): val(a), cnt(b){
}
};
struct cmp{
bool operator()(const Node& a, const Node& b){
return a.cnt < b.cnt;//按照cnt的降序排列
}
};
struct Node1{
int val;
int cnt;
Node1(int a, int b): val(a), cnt(b){
}
bool operator<(const Node1& a)const{
return cnt < a.cnt;//降序排列
}
};
int main(){
//方法一，定义仿函数用来对自定义类型的比较
priority_queue<Node, vector<Node>, cmp> pq;
//方法二，在自定义类型中重载小于比较运算符
priority_queue<Node1, vector<Node1>> pq1;
//测试仿函数
cout << "测试仿函数" << endl;
pq.push(Node(1, 4));
pq.push(Node(2, 9));
pq.push(Node(3, 1));
pq.push(Node(4, 10));
while(!pq.empty()){
cout << pq.top().val << " " << pq.top().cnt << endl;
pq.pop();
}
//测试自定义比较运算符
cout << "测试自定义比较运算符" << endl;
pq1.push(Node1(1, 4));
pq1.push(Node1(2, 9));
pq1.push(Node1(3, 1));
pq1.push(Node1(4, 10));
while(!pq1.empty()){
cout << pq1.top().val << " " << pq1.top().cnt << endl;
pq1.pop();
}
return 0;
}
operation result:
测试仿函数
4 10
2 9
1 4
3 1
测试自定义比较运算符
4 10
2 9
1 4
3 1
How to handle custom types of comparison functions in map
#include <bits/stdc++.h>
using namespace std;
struct Node{
int val;
int cnt;
Node(int a, int b): val(a), cnt(b){
}
};
struct cmp{
bool operator()(const Node& a, const Node& b){
return a.cnt < b.cnt;//按照cnt的升序排列
}
};
struct Node1{
int val;
int cnt;
Node1(int a, int b): val(a), cnt(b){
}
bool operator<(const Node1& a)const{
return cnt < a.cnt;//升序排列
}
};
int main(){
//方法一，定义仿函数用来对自定义类型的比较
map<Node, int, cmp> m;
//方法二，在自定义类型中重载小于比较运算符
map<Node1, int> m1;
//测试仿函数
cout << "测试仿函数" << endl;
m[Node(1,4)] = 1;
m[Node(2,10)] = 1;
m[Node(3,7)] = 1;
m[Node(-1,15)] = 1;
for(auto temp : m){
cout << temp.first.val << " " << temp.first.cnt << endl;
}
//测试自定义比较运算符
cout << "测试自定义比较运算符" << endl;
m1[Node1(1,4)] = 1;
m1[Node1(2,10)] = 1;
m1[Node1(3,7)] = 1;
m1[Node1(-1,15)] = 1;
for(auto temp : m1){
cout << temp.first.val << " " << temp.first.cnt << endl;
}
return 0;
}
operation result:
测试仿函数
1 4
3 7
2 10
-1 15
测试自定义比较运算符
1 4
3 7
2 10
-1 15
Special attention:
using the same way to define functors and overloading the comparison operators in the class, the result is one in ascending order and the other in descending order
sort function, for comparison of custom types
#include <bits/stdc++.h>
using namespace std;
/***********************************************************************/
struct Node{
int val;
int cnt;
Node(int a, int b): val(a), cnt(b){
}
};
struct cmp{
bool operator()(const Node& a, const Node& b){
return a.cnt < b.cnt;//按照cnt的升序排列
}
};
bool cmp1(const Node& a, const Node& b){
return a.cnt < b.cnt;
}
/**********************************************************/
struct Node1{
int val;
int cnt;
Node1(int a, int b): val(a), cnt(b){
}
bool operator<(const Node1& a)const{
return cnt < a.cnt;//升序排列
}
};
int main(){
vector<Node> nums;
nums.push_back(Node(1, 4));
nums.push_back(Node(3, 14));
nums.push_back(Node(2, 9));
nums.push_back(Node(5, 3));
//sort(nums.begin(), nums.end(), cmp()); //采用仿函数的比较形式，注意这里的cmp要加上括号
sort(nums.begin(), nums.end(), cmp1);//采用普通比较函数的形式
for(auto t : nums){
cout << t.val << " " << t.cnt << endl;
}
cout << "重载自定义类型的比较运算符" << endl;
vector<Node1> nums1;
nums1.push_back(Node1(1, 4));
nums1.push_back(Node1(3, 14));
nums1.push_back(Node1(2, 9));
nums1.push_back(Node1(5, 3));
sort(nums1.begin(), nums1.end());
for(auto t : nums1){
cout << t.val << " " << t.cnt << endl;
}
return 0;
}
operation result:
5 3
1 4
2 9
3 14
重载自定义类型的比较运算符
5 3
1 4
2 9
3 14