hdu Matrix Multiplication 写一个类似哈希函数的东西一切就解决了。
Problem Description
You are given three n × n matrices A, B and C. Does the equation A × B = C hold true?
Input
The first line of input contains a positive integer n (n ≤ 500) followed by the the three matrices A, B and C respectively. Each matrix's description is a block of n × n integers.
It guarantees that the elements of A and B are less than 100 in absolute value and elements of C are less than 10,000,000 in absolute value.
Output
Output "YES" if the equation holds true, otherwise "NO".
Sample Input
2
1 0
2 3
5 1
0 8
5 1
10 26
Sample Output
YES
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1 #include<iostream> 2 #include<string> 3 #include<cstring> 4 #include<cstdio> 5 #include<cmath> 6 #include<queue> 7 #include<algorithm> 8 #include<vector> 9 #define LL long long 10 using namespace std; 11 12 LL a[501][501],b[501][501],c[501][501]; 13 LL d[501],e[501],f[501],x[501]; 14 LL n,m,i,j,k; 15 int main() 16 { 17 while(scanf("%lld",&n)!=EOF) 18 { 19 for(i=0; i<n; i++) 20 for(j=0; j<n; j++) 21 scanf("%lld",&a[i][j]); 22 for(i=0; i<n; i++) 23 for(j=0; j<n; j++) 24 scanf("%lld",&b[i][j]); 25 for(i=0; i<n; i++) 26 for(j=0; j<n; j++) 27 scanf("%lld",&c[i][j]); 28 for(i=0; i<n; i++) 29 x[i]=i; 30 for(i=0; i<n; i++) 31 f[i]=e[i]=d[i]=0; 32 for(i=0; i<n; i++) 33 for(j=0; j<n; j++) 34 { 35 e[i]+=b[i][j]*x[j]; 36 f[i]+=c[i][j]*x[j]; 37 } 38 for(i=0; i<n; i++) 39 for(int j=0; j<n; j++) 40 d[i]+=a[i][j]*e[j]; 41 for(i=0; i<n; i++) 42 if(d[i]!=f[i]) break; 43 if(i<n) 44 puts("NO"); 45 else 46 puts("YES"); 47 } 48 return 0; 49 }