function<int(int,int)>
时间: 2023-12-26 19:05:05 浏览: 36
这是一个函数类型的定义,该函数类型名为“function”,它接受两个整型参数并返回一个整型值。可以使用该函数类型定义变量,例如:
```
function<int(int, int)> myFunc;
myFunc = [](int a, int b) { return a + b; };
int result = myFunc(2, 3); // result = 5
```
上述代码定义了一个名为“myFunc”的变量,它是一个函数类型,可以将一个 lambda 表达式赋值给它,并调用它来计算两个整数的和。
相关问题
修改以下代码#include "sortlevel.h" using namespace std; Compare<vector<int>> make_comp(list<sort_level> sortlevels) { vector<function<bool(vector<int>,vector<int>)>> func; for(auto sortlevel : sortlevels) { int i = sortlevel.column; switch (sortlevel.order) { case ASCEND: auto cmp = [i](vector<int> a,vector<int> b) { return a[i] < b[i]; }; func.push_back(cmp); break; case DESCEND: auto cmp = [i](vector<int> a,vector<int> b) { return a[i] < b[i]; }; func.push_back(cmp); break; default: break; } } Compare<vector<int>> comp(func); return comp; }
#include "sortlevel.h"
using namespace std;
Compare<vector<int>> make_comp(list<sort_level> sortlevels) {
vector<function<bool(vector<int>,vector<int>)>> func;
for(auto sortlevel : sortlevels) {
int i = sortlevel.column;
switch (sortlevel.order) {
case ASCEND:
func.push_back([i](vector<int> a,vector<int> b) { return a[i] < b[i]; });
break;
case DESCEND:
func.push_back([i](vector<int> a,vector<int> b) { return a[i] > b[i]; });
break;
default:
break;
}
}
Compare<vector<int>> comp(func);
return comp;
}
修改后的代码中,在 switch 语句中,我们使用 lambda 表达式来定义比较函数 cmp,而不是在每个 case 中都定义一个 cmp。此外,对于降序排序,我们修改了 lambda 表达式的实现,使其返回 a[i] > b[i]。最后,我们直接将 lambda 表达式 push_back 到 vector 中,避免了中间变量 cmp 的使用。
priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq
This is a declaration of a priority queue in C++ that stores pairs of integers. The priority queue is implemented using a min-heap, which means that the smallest element will have the highest priority. The first integer in the pair is the priority and the second integer is the value.
The syntax for declaring a priority queue in C++ is:
priority_queue<data_type, container_type, comparison_function>
In this case, the data type is a pair of integers (pair<int, int>), the container type is a vector (vector<pair<int, int>>), and the comparison function is the default less-than operator (>).
However, in order to implement a min-heap, we need to use the greater-than operator (<) instead. So we pass greater<pair<int, int>> as the comparison function.
Overall, this priority queue will store pairs of integers in ascending order of their first element. If two pairs have the same first element, then they will be ordered based on their second element in ascending order as well.