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hdu 4920 Matrix multiplication
Matrix multiplication
Time Limit: 4000/2000 MS (Java/Others) Memory Limit: 131072/131072 K (Java/Others)Total Submission(s): 334 Accepted Submission(s): 112
Problem Description
Given two matrices A and B of size n×n, find the product of them.
bobo hates big integers. So you are only asked to find the result modulo 3.
bobo hates big integers. So you are only asked to find the result modulo 3.
Input
The input consists of several tests. For each tests:
The first line contains n (1≤n≤800). Each of the following n lines contain n integers -- the description of the matrix A. The j-th integer in the i-th line equals Aij. The next n lines describe the matrix B in similar format (0≤Aij,Bij≤109).
The first line contains n (1≤n≤800). Each of the following n lines contain n integers -- the description of the matrix A. The j-th integer in the i-th line equals Aij. The next n lines describe the matrix B in similar format (0≤Aij,Bij≤109).
Output
For each tests:
Print n lines. Each of them contain n integers -- the matrix A×B in similar format.
Print n lines. Each of them contain n integers -- the matrix A×B in similar format.
Sample Input
1 0 1 2 0 1 2 3 4 5 6 7
Sample Output
0 0 1 2 1
Author
Xiaoxu Guo (ftiasch)
Source
2014 Multi-University Training Contest 5
题解及代码:
/* 签到题,简单的矩阵相乘,注意元素0的处理就不会超时了。 */ #include <iostream> #include <cstdio> #include <cstring> using namespace std; const int mod=3; int a[810][810],b[810][810]; int temp[810][810]; void multiple(int n,int p) { int i,j,k; for(i=0; i<n; i++) for(j=0; j<n; j++) { if(a[i][j]!=0) for(k=0; k<n; k++) temp[i][k]=(temp[i][k]+a[i][j]*b[j][k])%p; } for(int i=0;i<n;i++) { for(int j=0;j<n;j++) if(j==0) printf("%d",temp[i][j]); else printf(" %d",temp[i][j]); puts(""); } } void init(int n) { memset(temp,0,sizeof(temp)); for(int i=0;i<n;i++) { for(int j=0;j<n;j++) { scanf("%d",&a[i][j]); a[i][j]%=3; } } for(int i=0;i<n;i++) { for(int j=0;j<n;j++) { scanf("%d",&b[i][j]); b[i][j]%=3; } } } int main() { int n; while(cin>>n) { init(n); multiple(n,mod); } return 0; }
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