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 "); 47 else 48 printf("NO "); 49 } 50 return 0; 51 }