c语言的题，请友友们解答

Question

刚开始学习c语言，这几个题我不会，还没有掌握，请友友们解答！

Answer 1

1009 Code

有可能超时，应该还有优化的空间。

#include<stdio.h>

int main(){

    int T;
    scanf("%d", &T);

    for( int t = 0; t < T ;t++ ) {
        unsigned long long x;
        unsigned int n;
        scanf("%lld %d", &x, &n);

        unsigned long long Gx = x;
        for( int i=0; i < n; i++) {
            unsigned long long tmp = Gx;
            unsigned long long fx = 1;
            while ( tmp != 0 )
            {
                fx *= tmp % 10;
                tmp /= 10;
            }
            Gx = fx;
            if( Gx < 10 ) {
                break;
            }
        }
        
        printf("%lld\n", Gx);
    }

    return 0;
}

1018 Code

#include<stdio.h>

int main(){

    int N;
    scanf("%d", &N);
    while ( N-- )
    {
        int a,b;
        scanf("%d %d", &a, &b);

        int maxL = a < b? a : b;
        unsigned long long cnt = 0;
        for( int t = 0; t < maxL ; t++ ) {
            cnt += (a - t) * (b - t);
        }
        printf("%lld\n", cnt);
    }
    return 0;
    
}

1019 code

```c

#include<stdio.h>
#include<math.h>

int main(){

    int T;
    scanf("%d", &T);
    while ( T-- )
    {

        int Ax,Ay,Bx,By,Cx,Cy;
        scanf("%d %d %d %d %d %d", &Ax,&Ay,&Bx,&By,&Cx,&Cy);

        double area = 0;

        if( Ax == Bx || Ay == By ) {
            area = abs( (Ax-Cx)*(Ay-Cy) );
        } else{
            float cosAg =  ( (Bx-Ax)*(Cx-Ax) + (By-Ay)*(Cy-Ay) ) / ( sqrt( (Cx-Ax)*(Cx-Ax) + (Cy-Ay)*(Cy-Ay) ) * sqrt( (Bx-Ax)*(Bx-Ax) + (By-Ay)*(By-Ay) ) );
            area = abs( ( (Cx-Ax)*(Cx-Ax) + (Cy-Ay)*(Cy-Ay) ) * sqrt( 1 - cosAg* cosAg ) * cosAg );
        }

        printf("%.1f\n", area);
    }
    return 0;
    
}

```