POJ 3318 Matrix Multiplication(随机算法)

题目链接

随机算法使劲水...srand((unsigned)time(0))比srand(NULL)靠谱很多，可能是更加随机。

 

 1 #include <cstdio>

 2 #include <cstdlib>

 3 #include <cstring>

 4 #include <map>

 5 #include <ctime>

 6 #include <cmath>

 7 using namespace std;

 8 #define LL __int64

 9 int a[501][501],b[501][501],c[501][501];

10 int main()

11 {

12     int i,j,k,flag,n;

13     srand((unsigned)time(0));

14     while(scanf("%d",&n)!=EOF)

15     {

16         for(i = 1; i <= n; i ++)

17         {

18             for(j = 1; j <= n; j ++)

19                 scanf("%d",&a[i][j]);

20         }

21         for(i = 1; i <= n; i ++)

22         {

23             for(j = 1; j <= n; j ++)

24                 scanf("%d",&b[i][j]);

25         }

26         for(i = 1; i <= n; i ++)

27         {

28             for(j = 1; j <= n; j ++)

29                 scanf("%d",&c[i][j]);

30         }

31         flag = 1;

32         for(i = 1; i <= 40000&&flag; i ++)

33         {

34             LL temp = 0;

35             int x,y;

36             x = rand()%n + 1;

37             y = rand()%n + 1;

38             for(k = 1; k <= n; k ++)

39             {

40                 temp += a[x][k]*b[k][y];

41             }

42             if(temp != c[x][y])

43                 flag = 0;

44         }

45         if(flag)

46             printf("YES\n");

47         else

48             printf("NO\n");

49     }

50     return 0;

51 }