Codeforces Round #447 (Div. 2) B. Ralph And His Magic Field(数学???)
2017-11-22 17:47
609 查看
题目链接:http://codeforces.com/contest/894/problem/B
你问我为什么B都不会,那我也是很绝望的,如果k=-1,n和m奇偶性不同,你会发现,如果满足每行都为-1,和满足每行都等于-1,整个矩阵的乘积是不同的,k=-1奇偶性不同是不存在解的,然后发现,一个(n-1)*(m-1)的矩阵可以任意填,然后通过那一行加一列选择1或者-1可以满足所有条件,然后分析一波发现,一行一列相交的元素只有那一种情况下会出现矛盾,所以,答案就是2^((n-1)*(m-1)),好难啊。。。
代码:
def qpow(a,b,mod):
ret=1
while(b!=0):
if (b&1)==1:
ret*=a
ret%=mod
a*=a
a%=mod
b/=2
return ret
n,m,k=map(int,raw_input().split())
if k==-1 and n%2!=m%2:
print 0
exit(0)
print qpow(2,(n-1)*(m-1),1000000007)
你问我为什么B都不会,那我也是很绝望的,如果k=-1,n和m奇偶性不同,你会发现,如果满足每行都为-1,和满足每行都等于-1,整个矩阵的乘积是不同的,k=-1奇偶性不同是不存在解的,然后发现,一个(n-1)*(m-1)的矩阵可以任意填,然后通过那一行加一列选择1或者-1可以满足所有条件,然后分析一波发现,一行一列相交的元素只有那一种情况下会出现矛盾,所以,答案就是2^((n-1)*(m-1)),好难啊。。。
代码:
def qpow(a,b,mod):
ret=1
while(b!=0):
if (b&1)==1:
ret*=a
ret%=mod
a*=a
a%=mod
b/=2
return ret
n,m,k=map(int,raw_input().split())
if k==-1 and n%2!=m%2:
print 0
exit(0)
print qpow(2,(n-1)*(m-1),1000000007)
相关文章推荐
- Codeforces Round #447 (Div. 2) B. Ralph And His Magic Field(数论,组合数学)
- 【Codeforces Round #447 (Div. 2) B】Ralph And His Magic Field
- Codeforces Round #447 (Div. 2) B. Ralph And His Magic Field(思维)
- Codeforces Round #447 (Div. 2) B. Ralph And His Magic Field
- codeforces B. Ralph And His Magic Field 数学题+快速幂
- Codeforces Round #447 (Div. 2) B. Ralph And His Magic Field
- Codeforces Round #447 (Div. 2) B. Ralph And His Magic Field 推规律+证明
- Codeforces Round #447 (Div. 2) B. Ralph And His Magic Field
- Codeforces 894 B. Ralph And His Magic Field
- codeforces 894B - Ralph And His Magic Field - [快速幂]
- Codeforces894B-Ralph And His Magic Field
- codeforces B - Ralph And His Magic Field
- Ralph And His Magic Field
- codeforces 894 B题 Ralph And His Magic Field(巧思)
- Codeforces Round #280 (Div. 2) E. Vanya and Field (数学GCD)
- Codeforces Round #447 (Div. 2) D. Ralph And His Tour in Binary Country(dfs)
- codeforces Round 447 div2 D Ralph And His Tour in Binary Country
- Codeforces Round #280 (Div. 2) E. Vanya and Field 数学
- Codeforces Round #280 (Div. 2) E. Vanya and Field 数学
- Codeforces Round #369 (Div. 2) B. Chris and Magic Square【数学,模拟】