hdu 5630 Rikka with Chess【思维+递推】

Rikka with Chess

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 24    Accepted Submission(s): 22

Problem Description

Yuta gives Rikka a chess board of size n×m.

As we all know, on a chess board, every cell is either black or white and every two cells that share a side have different colors.

Rikka can choose any rectangle formed by board squares and perform an inversion, every white cell becomes black, and vice versa.

Rikka wants to turn all cells into the same color, please tell Rikka the minimal number of inversions she need to achieve her goal.

 

Input

The first line contains a number T(T≤10) ——The number of the testcases.

Each testcase contains two numbers n,m(n≤109,m≤109).

 

Output

For each testcase, print a single number which represents the answer.

 

Sample Input

31 22 23 3

 

Sample Output

122

一道递推找规律的题。通过样例3我们得知，中间一排翻转然后中间一列翻转能够用两次就得到最终想要的结果、我们再多举出几个例子比如 2 4

我们能看的出来，先在最后一排翻转，然后第二列第四列翻转能够得到想要的结果，然后多枚举出来几个情况，递推能力强的小伙伴几分钟就看出来怎么做了~

AC代码：

#include<stdio.h>#include<string.h>#include<algorithm>#include<iostream>using namespace std;#define ll long long intint main(){    int t;    scanf("%d",&t);    while(t--)    {        ll n,m;        scanf("%I64d%I64d",&n,&m);        printf("%I64d\n",n/2+m/2);    }}