行列式计算器

 1 #include<cstdio>
 2 #include<cstdlib>
 3 #include<cmath>
 4 
 5 #define zero 1e-8
 6 
 7 double a[101][101];
 8 
 9 int main(void)
10 {
11   int x;
12   scanf("%d", &x);
13   for(int i = 1; i <= x; ++i)
14     for(int j = 1; j <= x; ++j)
15       scanf("%lf", &a[i][j]);
16   int flag = 0;
17   for(int i = 1; i < x; ++i){
18     if(fabs(a[i][i]) <= zero)
19       for(int j = i+1; j <= x; ++j)
20     if(fabs(a[j][i]) > zero){
21       flag++;
22       for(int k = 2, l; k <= x; ++k){
23         l = a[i][k];
24         a[i][k] = a[j][k];
25         a[j][k] = l;
26       }
27       break;
28     }
29     if(fabs(a[i][i]) > zero)
30       for(int j = i+1; j <= x; ++j)
31     if(fabs(a[j][i]) > zero){
32       double l = a[j][i] / a[i][i];
33       for(int k = i; k <= x; ++k) a[j][k] -= a[i][k] * l;
34     }
35   }
36   /*
37   for(int i = 1; i <= x; ++i){
38     for(int j = 1; j <= x; ++j)
39       printf("%lf ", a[i][j]);
40     printf("\n");
41   }
42   */
43   double ans = a[1][1] * (1 - 2*(1 && flag));
44   for(int i = 2; i <= x; ++i) ans *= a[i][i];
45   printf("%d", (int)round(ans));
46   return 0;
47 }