例题8-4(uva-11134)

最新推荐文章于 2021-05-18 14:52:46 发布

原创最新推荐文章于 2021-05-18 14:52:46 发布 · 70 阅读

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这篇博客探讨了一种高效算法，用于处理线性区间的覆盖问题。通过排序和迭代，算法确保了所有区间有效覆盖且无重叠。在输入n个区间后，程序检查并更新每个区间的起始和结束点，最终输出可行的解决方案或返回'IMPOSSIBLE'。

#include <iostream>
#include <istream>
#include <sstream>
#include <vector>
#include <stack>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
#include <algorithm>
#include <numeric>
#include <chrono>
#include <ctime>
#include <cmath>
#include <cctype>
#include <string>
#include <cstdio>
#include <iomanip>


#include <thread>
#include <mutex>
#include <condition_variable>
#include <functional>
#include <iterator>
using namespace std;
const int maxn = 5007;
struct Node {
	int first;
	int last;
	int id;
}nodex[maxn],nodey[maxn];

int n;

bool CmpCheck(const Node& a, const Node& b) {
	if (a.first != b.first) return a.first < b.first;
	return a.last < b.last;
}
bool CmpOut(const Node& a, const Node& b) {
	return a.id < b.id;
}
bool Check(Node * in) {
	sort(in + 1, in + n + 1, CmpCheck);

	for (int i = 1; i <= n; i++) {
		if (in[i].first > in[i].last || in[i].first > i || in[i].last < i) return false;
		in[i].first = i;
		in[i].last = i;
		int j = i + 1;
		for ( ;j<=n;j++)
		{
			if (in[j].first <= i) {
				in[j].first = i + 1;
			}else if(in[j].first > i + 1) break;
		}
		sort(in + i + 1, in + j, CmpCheck);
	}
	return true;
}

int main()
{
	while (cin >> n && n) {
		bool isok = true;
		for (int i = 1; i <= n; i++) {
			cin >> nodex[i].first  >> nodey[i].first >> nodex[i].last >> nodey[i].last;
			nodex[i].id = i;
			nodey[i].id = i;
		}

		if (Check(nodex) && Check(nodey)) {
			sort(nodex + 1, nodex + n + 1, CmpOut);
			sort(nodey + 1, nodey + n + 1, CmpOut);
			for (int i = 1;i<=n;i++)
				cout << nodex[i].first << " " << nodey[i].first << endl;
		}
		else cout << "IMPOSSIBLE" << endl;
	}
	return 0;
}