Krydom: 暁の水平线に胜利を刻むのです

ソロモンの悪夢、見せてあげる!

@krydom1年前

07/14
15:32
单调栈/队列

[bzoj 3314] [Usaco2013 Nov]Crowded Cows

♦♦♦♦♦♦   Description   ♦♦♦♦♦♦

Farmer John's N cows (1 <= N <= 50,000) are grazing along a one-dimensional fence. Cow i is standing at location x(i) and has height h(i) (1 <= x(i),h(i) <= 1,000,000,000). A cow feels "crowded" if there is another cow at least twice her height within distance D on her left, and also another cow at least twice her height within distance D on her right (1 <= D <= 1,000,000,000). Since crowded cows produce less milk, Farmer John would like to count the number of such cows. Please help him.

N头牛在一个坐标轴上,每头牛有个高度。现给出一个距离值D。

如果某头牛在它的左边,在距离D的范围内,如果找到某个牛的高度至少是它的两倍,且在右边也能找到这样的牛的话。则此牛会感觉到不舒服。

问有多少头会感到不舒服。

♦♦♦♦♦♦   Input   ♦♦♦♦♦♦

* Line 1: Two integers, N and D.

* Lines 2..1+N: Line i+1 contains the integers x(i) and h(i). The locations of all N cows are distinct.

 

♦♦♦♦♦♦   Output   ♦♦♦♦♦♦

* Line 1: The number of crowded cows.

♦♦♦♦♦♦   Sample Input   ♦♦♦♦♦♦

6 4
10 3
6 2
5 3
9 7
3 6
11 2

♦♦♦♦♦♦   Sample Output   ♦♦♦♦♦♦

2

♦♦♦♦♦♦   Hint   ♦♦♦♦♦♦

♦♦♦♦♦♦   题解  ♦♦♦♦♦♦

从左往右和从右往左各维护一个单调队列就行了

 

[bzoj 3314] [Usaco2013 Nov]Crowded Cows