我说,如果我们要使用 STL 和 C++ .. 让我们以现代风格编写它并真正使用 STL。
我尝试使用现代 c++11 解决这个问题:
#include <vector>
#include <iostream>
#include <algorithm>
typedef std::vector<int> ArrayInt;
typedef std::vector< std::vector<int> > ArrayData;
bool compare(const ArrayInt& a, const ArrayInt& b) {
std::cout << &(a) << ' ' << &(b) << std::endl;
int sumA = std::accumulate(a.begin(), a.end(), 0);
int sumB = std::accumulate(b.begin(), b.end(), 0);
return sumA < sumB;
}
int main(int argc, char** argv) {
ArrayData array = {
{1,2,4,0,3,7,6,8,3,3},
{13,2,4,0,3,7,6,8,3,3},
{10,2,4,0,3,7,6,8,3,3},
{1,2,4,0,3,7,6,8,3,3},
{16,2,4,0,3,7,6,8,3,3},
{1,2,400,0,3,7,6,8,3,3},
{1,2,4,0,3,7,6,8,3,3},
{120,2,4,0,3,7,6,8,3,3},
{1,2,4,0,3,7,6,8,3,3},
{1,2,4,0,3,7,6,8,3,3}
};
std::sort(array.begin(), array.end(), compare);
for (auto row : array) {
for (int num : row)
std::cout << num << ' ';
std::cout << std::endl;
}
}
它使用累积来对每个子数组求和,并对总和进行排序.. 它的效率非常低,因为它必须多次对同一行求和.. 但它只是为了展示自定义比较函数。
作为练习,我编写了这个版本,它使用异步将求和部分分配到任何可用的内核上,以便在排序之前进行求和。很抱歉,话题有点跑题了。我希望它对某些人仍然有用:
#include <vector>
#include <iostream>
#include <algorithm>
#include <future>
typedef std::vector<int> IntRow;
typedef std::pair<int, IntRow> DataRow;
typedef std::vector<DataRow> DataTable;
int main(int argc, char** argv) {
// Holds the sum of each row, plus the data itself
DataTable array = {
{0, {1,2,4,0,3,7,6,8,3,3}},
{0, {13,2,4,0,3,7,6,8,3,3}},
{0, {10,2,4,0,3,7,6,8,3,3}},
{0, {1,2,4,0,3,7,6,8,3,3}},
{0, {16,2,4,0,3,7,6,8,3,3}},
{0, {1,2,400,0,3,7,6,8,3,3}},
{0, {1,2,4,0,3,7,6,8,3,3}},
{0, {120,2,4,0,3,7,6,8,3,3}},
{0, {1,2,4,0,3,7,6,8,3,3}},
{0, {1,2,4,0,3,7,6,8,3,3}}
};
// Make use of multiple cores if it's efficient enough
// get the sum of each data row
std::vector<std::future<int>> sums(array.size());
auto next = sums.begin();
for (auto& row : array)
*next++ = std::async([](const IntRow& row) { return std::accumulate(row.begin(), row.end(), 0); }, row.second);
// Get the results
auto nextRow = array.begin();
for (auto& sum: sums)
(*nextRow++).first = sum.get();
// Sort it
std::sort(array.begin(), array.end(),
[](const DataRow& a, const DataRow& b) { return a.first < b.first; });
// Print it
for (auto row : array) {
for (int num : row.second)
std::cout << num << ' ';
std::cout << std::endl;
}
}
它需要使用 pthread 库或类似库进行编译:
g++ -O6 sort.cpp --std=c++11 -g -lpthread