ACQUIRE - Land Acquisition

Gold Problem Land Acquisition [Paul Christiano, 2007]

Farmer John is considering buying more land for the farm and has his eye on N (1 <= N <= 50,000) additional rectangular plots, each with integer dimensions (1 <= width_i <= 1,000,000; 1 <= length_i <= 1,000,000).

If FJ wants to buy a single piece of land, the cost is $1/square unit, but savings are available for large purchases. He can buy any number of plots of land for a price in dollars that is the width of the widest plot times the length of the longest plot. Of course, land plots cannot be rotated, i.e., if Farmer John buys a 3x5 plot and a 5x3 plot in a group, he will pay 5x5=25.

FJ wants to grow his farm as much as possible and desires all the plots of land. Being both clever and frugal, it dawns on him that he can purchase the land in successive groups, cleverly minimizing the total cost by grouping various plots that have advantageous width or length values.

Given the number of plots for sale and the dimensions of each, determine the minimum amount for which Farmer John can purchase all

Input

  • Line 1: A single integer: N
  • Lines 2..N+1: Line i+1 describes plot i with two space-separated integers: width_i and length_i

Output

  • Line 1: The minimum amount necessary to buy all the plots.

Sample

Input:
4
100 1
15 15
20 5
1 100

Output:
500

Explanation

There are four plots for sale with dimensions as shown.

The first group contains a 100x1 plot and costs 100. The next group contains a 1x100 plot and costs 100. The last group contains both the 20x5 plot and the 15x15 plot and costs 300. The total cost is 500, which is minimal.


Added by:Hasan Jaddouh
Date:2013-05-31
Time limit:1s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ASM64
Resource:USACO Mar08

hide comments
2018-11-09 04:11:48
Getting TLE even after removing irrelevant rectangles and applying dp solution O(n^2).
2018-09-11 16:19:29
AC in 1 go, test cases are correct. Check your code again and again until you find the bug.
2018-06-03 13:14:31
WA!!! I followed the method given on Wiki, convex-hull-trick dp solution
2018-04-11 19:40:03
OK friends if you are getting WA these are the test cases: http://contest.usaco.org/MAR08.htm. Hope that helps
2018-03-07 14:55:47
I submitted the solution given in the wcipeg article and got WA.
2018-02-03 01:45:00
Good convex hull trick!
2017-07-30 21:29:22
Finally accepted!!o(n2) solution.useful link https://wcipeg.com/wiki/Convex_hull_trick for solving
2017-06-21 10:44:47
Removed irrelevant rectangles and O(n^2) DP passed.
2017-06-08 06:50:38
I tried both dp and convex hull technique, only latter gives AC (dp solution passes all test cases of spoj toolkit), dp solution gives WA.
2016-09-15 13:12:24
I haven't read convex hull trick and am trying to pass a O(n^2) solution, but am getting WA.
My code gives the correct answer for all test cases on spojtoolkit.com Kindly help me with a few peculiar test cases.
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