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

void scale(int n,double v[],double alpha){
    for(int i=0;i<n;i++){
        v[i]*=alpha;
    }
}
void eliminate(int n,double v1[],
    double v2[],double alpha){
    for(int i=0;i<n;i++){
        v1[i]+=alpha*v2[i];
    }
}
void swap(int n,double v1[],double v2[]){
    for(int i=0;i<n;i++){
        double t=v1[i]; v1[i]=v2[i]; v2[i]=t;
    }
}
void matprint(int n,double A[n][n]){
    for(int i=0;i<n;i++){
        for(int j=0;j<n;j++){
            printf("%g ",A[i][j]);
        }
        printf("\n");
    }
}
void lufact(int n,double A[n][n]){
    for(int j=0;j<n-1;j++){
        for(int i=j+1;i<n;i++){
            double alpha=-A[i][j]/A[j][j];
            printf("r%d <- r%d + %g r%d\n",
                i,i,alpha,j);
            eliminate(3,A[i],A[j],alpha);
        }
    }
}
double A[3][3] = {{3,1,8},{2,4,7},{1,2,3}};

int main(){
    matprint(3,A);
    lufact(3,A);
    matprint(3,A);
    return 0;
}