Matrix God 随机化构造矩阵降维

https://codeforces.com/gym/101341/problem/I

题意:

给定三个矩阵ABC,问A*b是否等于c

代码:

 1 #include <stdio.h>
 2 #include <string.h>
 3 #include <stdlib.h>
 4 
 5 long long mod = 1e9+7;
 6 
 7 long long a[1005][1005], b[1005][1005], c[1005][1005];
 8 long long re1[1005], re2[1005], re3[1005];
 9 long long ran[1005];
10 
11 int main()
12 {
13     long long n, i, j;
14     scanf("%lld", &n);
15     for(i=0;i<n;i++)
16     {
17         for(j=0;j<n;j++)
18         {
19             scanf("%lld", &a[i][j]);
20         }
21     }
22     for(i=0;i<n;i++)
23     {
24         for(j=0;j<n;j++)
25         {
26             scanf("%lld", &b[i][j]);
27         }
28     }
29 
30     for(i=0;i<n;i++)
31     {
32         for(j=0;j<n;j++)
33         {
34             scanf("%lld", &c[i][j]);
35         }
36     }
37     for(i=0;i<n;i++)
38     {
39         ran[i] = rand() % 100 + 1;
40     }
41     //cheng 1 1 1 1 1
42     for(j=0;j<n;j++)
43     {
44         re1[j] = 0;
45         for(i=0;i<n;i++)
46         {
47             re1[j] = (re1[j] + ran[i] * a[i][j]) % mod;
48         }
49     }
50 
51     for(j=0;j<n;j++)
52     {
53         re2[j] = 0;
54         for(i=0;i<n;i++)
55         {
56             re2[j] = (re2[j] + re1[i] * b[i][j]) % mod;
57         }
58     }
59 
60     for(j=0;j<n;j++)
61     {
62         re3[j] = 0;
63         for(i=0;i<n;i++)
64         {
65             re3[j] = (re3[j] + ran[i] * c[i][j]) % mod;
66         }
67     }
68 
69     for(i=0;i<n;i++)
70     {
71         if(re2[i]!=re3[i]) break;
72     }
73     if(i<n) printf("NO\n");
74     else printf("YES\n");
75     return 0;
76 }
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