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Description

Problem E: Chainsaw Massacre

Background 

As every year the Canadian Lumberjack Society has just held its annual woodcutting competition and the national forests between Montreal and Vancouver are devastated. Now for the social part!In order to lay out an adequate dance floor for the evening partythe organizing committee is looking for a large rectangular area without trees. Naturally, all lumberjacks are already drunk and nobody wants to take the risk of having any of them operate a chainsaw.

The Problem 

The Input 

The first line of the input specifies the number of scenarios. For each scenario, the first line provides the length l and widthw of the area in meters (,both integers). Each ofthe following lines describes either a single tree, or a line of treesaccording to one of the following formats:

• 1 x y, where the ``one‘‘ characterizes a single tree, and x and y provide its coordinates in meters with respect to the upper leftcorner.
• k x y dx dy, where k>1 provides the number of trees in a line withcoordinates .
• 0 denotes the end of the scenario.

The Output 

For each scenario print a line containing the maximum size of the dance floor measured in square meters.

Sample Input 

2
2 3
0
10 10
2 1 1 8 0
2 1 9 8 0
0

Sample Output 

6
80

题意：平面上有n棵树，找出一个内部没有树的，面积最大的矩形

思路：以y坐标排序然后扫描，每次先扫到一棵树就可以知道它与上一棵树之间的距离，然后更新统计每个x坐标的最左边和最右边，每次都计算一次

#include <iostream>
#include <cstring>
#include <algorithm>
#include <cstdio>
#include <map>
#include <vector>
using namespace std;
const int maxn = 10010;

int h[maxn], l[maxn], r[maxn];
int n, m, ans;
map<int, vector<int> > tree;

void check() {
	for (int i = 0, j = n; i <= n; i++, j--) {
		for (l[i] = i; l[i] > 0 && h[l[i]-1] >= h[i]; )
			l[i] = l[l[i]-1];
		for (r[j] = j; r[j] < n && h[r[j]+1] >= h[j]; )
			r[j] = r[r[j]+1];
	}
}

void cal() {
	for (int i = 0; i <= n; i++) {
		int tmp = h[i] * (r[i] - l[i] + 2);
		ans = max(ans, tmp);
	}
}

int main() {
	int t;
	scanf("%d", &t);
	while (t--) {
		tree.clear();
		scanf("%d%d", &n, &m);
		int op, x, y, dx, dy;
		while (1) {
			scanf("%d", &op);
			if (op == 0) 
				break;
			else if (op == 1) {
				scanf("%d%d", &x, &y);
				tree[y].push_back(x);
			}
			else {
				scanf("%d%d%d%d", &x, &y, &dx, &dy);
				for (int i = 0; i < op; i++) {
					tree[y].push_back(x);
					y += dy, x += dx;
				}
			}
		}
		tree[m];
		ans = max(n, m);
		int last = 0;
		memset(h, 0, sizeof(h));
		map<int, vector<int> >::iterator it;
		for (it = tree.begin(); it != tree.end(); it++) {
			int d = it->first - last;
			last += d;
			for (int i = 1; i < n; i++)
				h[i] += d;
			check();
			cal();
			vector<int> tmp = it->second;
			for (int i = 0; i < tmp.size(); i++)
				h[tmp[i]] = 0;
		}
		printf("%d\n", ans);
	}
	return 0;
}

UVA - 10043 Chainsaw Massacre,布布扣,bubuko.com

UVA - 10043 Chainsaw Massacre

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原文地址：http://blog.csdn.net/u011345136/article/details/38457259