UVA_10020_Minimal coverage

#include<iostream>
#include<sstream>
#include<string>
#include<vector>
#include<list>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<algorithm>
#pragma warning(disable:4996)
#include<cstdio>
#include<cstdlib>
using std::cin;
using std::cout;
using std::endl;
using std::stringstream;
using std::string;
using std::vector;
using std::list;
using std::pair;
using std::set;
using std::multiset;
using std::map;
using std::multimap;
using std::stack;
using std::queue;
using std::priority_queue;
vector<int> dfs(vector<int>&line, const vector<pair<int, int>>&segment, int i)
{
vector<int>count;
for (; i < segment.size(); i++)
{
vector<int>temp;
//如果除去这个段，仍能保证区间上所有数都被覆盖
if (std::all_of(line.begin() + segment[i].first, line.begin() + segment[i].second + 1, [](int i) {return i >1; }))
{
//那么区间的段上的都-1
for (int j = segment[i].first; j <= segment[i].second; j++)
{
line[j]--;
}
temp = dfs(line, segment, i + 1);
temp.push_back(i);
//回溯--恢复现场
for (int j = segment[i].first; j <= segment[i].second; j++)
{
line[j]++;
}
}
count = count.size() > temp.size() ? count : temp;
}
return count;
}
int main()
{
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
int T;
while (cin >> T)
{
while (T--)
{
int n;
if (cin >> n)
{
;
}
else
{
break;
}
vector<pair<int, int>>segment;
map<pair<int, int>, pair<int, int>>Map;
int left, right;
while (cin >> left >> right)
{
if (!left&&!right)
{
break;
}
if (right<0 || left>n)
{
continue;
}
segment.push_back({ std::max(0,left),std::min(n,right) });
Map.insert({ { std::max(0,left),std::min(n,right) },{ left,right } });
}
std::sort(segment.begin(), segment.end());
auto iter = std::unique(segment.begin(), segment.end());
segment.resize(iter - segment.begin());
vector<int>line(n + 1);
for (size_t i = 0; i < segment.size(); i++)
{
for (left = segment[i].first; left <= segment[i].second; left++)
{
line[left]++;
}
}
if (std::any_of(line.begin(), line.end(), [](int i) {return i == 0; }))
{
cout << '0' << endl;
if (T)
{
cout << endl;
}
continue;
}
auto count = dfs(line, segment, 0);
cout << segment.size() - count.size() << endl;
vector<bool>hash(segment.size());
for (size_t i = 0; i < count.size(); i++)
{
hash[count[i]] = true;
}
for (size_t i = 0; i < hash.size(); i++)
{
if (!hash[i])
{
cout << Map[segment[i]].first << ' ' << Map[segment[i]].second << endl;
}
}
if (T)
{
cout << endl;
}
}
}
return 0;
}