2013秋13级预备队集训练习4 --E - Searching for Nessy

Searching for Nessy

The Loch Ness Monsteris a mysterious and unidentified animal said to inhabit Loch Ness, 
a large deep freshwater loch near the city of Inverness in northern Scotland. Nessie is usually categorized as a type of lake monster.
http://en.wikipedia.org/wiki/Loch_Ness_Monster

In July 2003, the BBC reported an extensive investigation of Loch Ness by a BBC team, using 600 separate sonar beams, found no trace of any ¨sea monster¨ (i.e., any large animal, known or unknown) in the loch. The BBC team concluded that Nessie does not exist. Now we want to repeat the experiment.

Given a grid of n rows and m columns representing the loch, 6n, m10000, find the minimum number s of sonar beams you must put in the square such that we can control every position in the grid, with the following conditions:

• one sonar occupies one position in the grid; the sonar beam controls its own cell and the contiguous cells;
• the border cells do not need to be controlled, because Nessy cannot hide there (she is too big).

For example,

where X represents a sonar, and the shaded cells are controlled by their sonar beams; the last figure gives us a solution.

Input 

The first line of the input contains an integer, t, indicating the number of test cases. For each test case, there is a line with two numbers separated by blanks, 6n, m10000, that is, the size of the grid (n rows and m columns).

Output 

For each test case, the output should consist of one line showing the minimum number of sonars that verifies the conditions above.

Sample Input 

 
3
6 6
7 7
9 13

Sample Output 

 
4
4
12
#include <stdio.h>
int main()
{
    int i , t , sum , n , m ;
    scanf("%d", &t);
    for(i = 1 ; i<= t ; i++)
    {
        scanf("%d %d", &n , &m);
        n = n-2 ; m = m-2 ;
        if(n%3!=0)
            n = n/3+1;
        else
            n = n/3;
        if(m%3!=0)
            m = m/3+1;
        else
            m = m/3;
        printf("%d\n", n*m);
    }
}