poj 2482 Stars in Your Window (线段树+平面扫描)
2017-04-12 19:35
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思路如果硬来肯定超时,所以线段树。数据处理,把x的点的亮度为k,x+w的亮度为-k,就是如果超出他的范围,就减去k,这样用线段树求区间最大值就行了
#include <iostream>
#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;
#define LL long long
#define MAX_N 10000
LL xs[MAX_N]; // 横坐标
LL ys[MAX_N]; // 纵坐标
int cs[MAX_N]; // 亮度
LL X[MAX_N * 2]; // 以每个星星为中心的窗口的左右横坐标
LL Y[MAX_N * 2]; // 以每个星星为中心的窗口的上下纵坐标
pair<pair<int, int>, pair<int, int> > event[MAX_N * 2]; // (x,add),(y1,y2) 一条线段,add为亮度
int node_value[MAX_N * 8], node_max[MAX_N * 8];
// 将[from, to]区间的节点对应的值增加v,同时维护节点对应区域的最大值
void add(int from, int to, int v, int i, int l, int r)
{
if (from <= l && r <= to)
{
node_value[i] += v;
node_max[i] += v;
return;
}
int m = (l + r) >> 1;
if (from <= m) add(from, to, v, i * 2, l, m);
if (m < to) add(from, to, v, i * 2 + 1, m + 1, r);
node_max[i] = max(node_max[i * 2], node_max[i * 2 + 1]) + node_value[i];
}
int main()
{
int n, W, H;
while (~scanf("%d%d%d", &n, &W, &H))
{
for (int i = 0; i < n; ++i)
{
scanf("%lld%lld%d", xs + i, ys + i, cs + i);
xs[i] *= 2;
// 乘2避免待会儿除法产生误差
ys[i] *= 2;
}
for (int i = 0; i < n; ++i)
{
X[i * 2] = xs[i] - W;
X[i * 2 + 1] = xs[i] + W;
Y[i * 2] = ys[i] - H;
Y[i * 2 + 1] = ys[i] - 1 + H;
}
sort(X, X + n * 2);
// 待会儿进行坐标压缩
sort(Y, Y + n * 2); // 为lower_bound做准备
for (int i = 0; i < n; ++i)
{
event[i * 2] = make_pair(make_pair(lower_bound(X, X + n * 2, xs[i] - W) - X, cs[i]), make_pair(lower_bound(Y, Y + n * 2, ys[i] - H) - Y, lower_bound(Y, Y + n * 2, ys[i] + H - 1) - Y));
event[i * 2 + 1] = make_pair(make_pair(lower_bound(X, X + n * 2, xs[i] + W) - X, -cs[i]), make_pair(lower_bound(Y, Y + n * 2, ys[i] - H) - Y, lower_bound(Y, Y + n * 2, ys[i] + H - 1) - Y));
}
sort(event, event + n * 2);
int ans = 0;
for (int i = 0; i < n * 2; i++)
{
add(event[i].second.first, event[i].second.second, event[i].first.second, 1, 0, n * 2);
ans = max(ans, node_max[1]);
}
printf("%d\n", ans);
}
return 0;
}
#include <iostream>
#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;
#define LL long long
#define MAX_N 10000
LL xs[MAX_N]; // 横坐标
LL ys[MAX_N]; // 纵坐标
int cs[MAX_N]; // 亮度
LL X[MAX_N * 2]; // 以每个星星为中心的窗口的左右横坐标
LL Y[MAX_N * 2]; // 以每个星星为中心的窗口的上下纵坐标
pair<pair<int, int>, pair<int, int> > event[MAX_N * 2]; // (x,add),(y1,y2) 一条线段,add为亮度
int node_value[MAX_N * 8], node_max[MAX_N * 8];
// 将[from, to]区间的节点对应的值增加v,同时维护节点对应区域的最大值
void add(int from, int to, int v, int i, int l, int r)
{
if (from <= l && r <= to)
{
node_value[i] += v;
node_max[i] += v;
return;
}
int m = (l + r) >> 1;
if (from <= m) add(from, to, v, i * 2, l, m);
if (m < to) add(from, to, v, i * 2 + 1, m + 1, r);
node_max[i] = max(node_max[i * 2], node_max[i * 2 + 1]) + node_value[i];
}
int main()
{
int n, W, H;
while (~scanf("%d%d%d", &n, &W, &H))
{
for (int i = 0; i < n; ++i)
{
scanf("%lld%lld%d", xs + i, ys + i, cs + i);
xs[i] *= 2;
// 乘2避免待会儿除法产生误差
ys[i] *= 2;
}
for (int i = 0; i < n; ++i)
{
X[i * 2] = xs[i] - W;
X[i * 2 + 1] = xs[i] + W;
Y[i * 2] = ys[i] - H;
Y[i * 2 + 1] = ys[i] - 1 + H;
}
sort(X, X + n * 2);
// 待会儿进行坐标压缩
sort(Y, Y + n * 2); // 为lower_bound做准备
for (int i = 0; i < n; ++i)
{
event[i * 2] = make_pair(make_pair(lower_bound(X, X + n * 2, xs[i] - W) - X, cs[i]), make_pair(lower_bound(Y, Y + n * 2, ys[i] - H) - Y, lower_bound(Y, Y + n * 2, ys[i] + H - 1) - Y));
event[i * 2 + 1] = make_pair(make_pair(lower_bound(X, X + n * 2, xs[i] + W) - X, -cs[i]), make_pair(lower_bound(Y, Y + n * 2, ys[i] - H) - Y, lower_bound(Y, Y + n * 2, ys[i] + H - 1) - Y));
}
sort(event, event + n * 2);
int ans = 0;
for (int i = 0; i < n * 2; i++)
{
add(event[i].second.first, event[i].second.second, event[i].first.second, 1, 0, n * 2);
ans = max(ans, node_max[1]);
}
printf("%d\n", ans);
}
return 0;
}
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