给出到不共线三点的距离，求这个点的坐标、随机生成浮点数

给出到不共线三点的距离，求这个点的坐标（公式是用 maple 求的）：

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

# define TRUE 1
# define FALSE 0

const double ERR = 0.05;

typedef char BOOL;

typedef struct {
    double x;
    double y;
}Point;


Point s1, s2, s3;               /* station  */
double d1, d2, d3;              /* distance */

BOOL read(void);
void solve(void);
void print_msg(void);
double dist(Point x, Point y);
char test_eps(double x, double y);
int isNegtive(double *var); 
void compute(Point p1, Point p2, double dt1, double dt2, Point *q1, Point *q2);

int main()
{
    freopen("in.txt", "r", stdin); 
    freopen("out.txt", "w", stdout);
    
    print_msg();    
    while (read() == TRUE)
    {
        solve();
    }
    
    return 0;
}

void print_msg(void)
{
    puts("输入三个基站坐标以及客户端到三个基站的距离，输出客户端的坐标。");
}

BOOL read(void)
{
    if (scanf("%lf%lf%lf%lf%lf%lf%lf%lf%lf", 
               &s1.x, &s1.y, &s2.x, &s2.y, &s3.x, &s3.y, &d1, &d2, &d3) == EOF)
    {
        
        /*printf("%lf %lf %lf %lf %lf %lf %lf %lf %lf\n", s1.x, s1.y, s2.x, s2.y, s3.x, s3.y, d1, d2, d3);*/
        return FALSE;
    }

    return TRUE;
}

double dist(Point a, Point b)
{
    return sqrt(pow(a.x-b.x, 2.0) + pow(a.y-b.y, 2.0) + 1e-6);
}

int isNegtive(double *var)            /* 判断一个 double 类型数是否为负、为零 */
{
    if ((*var)+1e-6 < 0) 
    {
        puts("data Error!");
        return -1;
    }
    else if (-1e-6<(*var) && (*var)<1e-6) 
    {
        (*var) = 0; 
        return 0;
    }
    return 1;
}

void compute(Point p1, Point p2, double dt1, double dt2, Point *q1, Point *q2)
{
    double r, R, h, k, delta;
    double r2, r4;
    double R2, R4;
    double k2, k4;
    double h2, h4;
    double xDen, yDen;
    double tmp;
    
    R = dt1;
    r = dt2;
    h = p2.x - p1.x;
    k = p2.y - p1.y;
    
    r2 = r * r;
    R2 = R * R;
    k2 = k * k;
    h2 = h * h;
    
    r4 = r2 * r2;
    R4 = R2 * R2;
    h4 = h2 * h2;
    k4 = k2 * k2;
    
    tmp = -1.0*h2*R4 - 2.0*h4*k2 - h2*k4 + 2.0*h4*R2 + 2.0*h4*r2
          - h2*r4 + 2.0*k2*r2*h2 + 2.0*h2*k2*R2 + 2.0*h2*r2*R2 - h2*h4;
    
    switch(isNegtive(&tmp))
    {
        case -1 : return;
        case  0 : delta = 0; break;
        case  1 : delta = sqrt(tmp + 1e-6); break;
    }
    
    yDen = 2.0 * (h2 + k2);
    xDen = h * yDen;
    
    if (-1e-6<yDen && yDen<1e-6)                    
    {
        /* 两个基站的纵坐标相同      */
        if ( isNegtive(&h) == 0) return ;
        (*q1).x = (*q2).x = (R2-r2+h2)/(2.0*h);
        
        tmp = R2 - pow((*q1).x, 2.0);
        if ( isNegtive(&tmp) == -1 ) return ;
                
        (*q1).y =  1.0*sqrt(tmp);
        (*q2).y = -1.0*sqrt(tmp);        
    } 
    else if (-1e-6<h && h<1e-6)                   
    {
        /* 两个基站的横坐标相同      */
        if ( isNegtive(&k) == 0) return ;        
        (*q1).y = (*q2).y = (R2-r2+k2)/(2.0*k);
                
        tmp = R2 - pow((*q1).y, 2.0);        
        if ( isNegtive(&tmp) == -1 ) return ;
        
        (*q1).x =  1.0*sqrt(tmp);
        (*q2).x = -1.0*sqrt(tmp);
    }
    else                                            
    {    
        /* 两个基站的横纵坐标都不相同 */
        tmp = -1.0*h4 - h2*k2 + h2*r2 - h2*R2;
        (*q1).x = ( -1.0*tmp - k*delta ) / xDen;
        (*q2).x = ( -1.0*tmp + k*delta ) / xDen;;
    
        tmp = -1.0*k*r2 + h2*k + k*k2 + k*R2;
        (*q1).y = ( 1.0*tmp + delta ) / yDen;
        (*q2).y = ( 1.0*tmp - delta ) / yDen;      
    }
    
    (*q1).x += p1.x;
    (*q1).y += p1.y;
    (*q2).x += p1.x;
    (*q2).y += p1.y;     
}

char test_eps(double x, double y)
{
    if (2.0*abs(x-y)/(x+y) < ERR+1e-6) return 1;
    return 0;
}

void solve(void)
{
    Point t1, t2;

    compute(s1, s2, d1, d2, &t1, &t2);
    /*
        printf("(%.3lf, %.3lf)\n", t1.x, t1.y);
        printf("(%.3lf, %.3lf)\n", t2.x, t2.y);
    */
    if (test_eps(dist(t1, s3), d3))
    {
        printf("客户端坐标a：");
        printf("(%.3lf, %.3lf)\n", t1.x, t1.y);
    }
    else if (test_eps(dist(t2, s3), d3))
    {
        printf("客户端坐标b：");
        printf("(%.3lf, %.3lf)\n", t2.x, t2.y);
    }
    else
    {
        puts("数据有误");
    }
}

随机生成不共线三点的坐标（浮点数）和一个点：

/* 随机生成数据 */

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

# define N 100          /* 随机生成 N 组数据 */ 
# define MOD 31723      /* 素数              */ 

typedef struct {
    double x;
    double y;
}Point;


Point s1, s2, s3, c;               /* station  */
double d1, d2, d3;                 /* distance */

double dist(Point a, Point b);

int rand_sgn(void)                      /* 随机生成符号 */
{
    return (rand()&0x1) ? 1:-1;
}

double rand_double(void)
{
    int den;
    
    while ((den=rand()%MOD) == 0) ;
    return rand_sgn()*(rand()%MOD)*1000.0/den;
}

void rand_Point(Point *p)
{
    (*p).x = rand_double();
    (*p).y = rand_double();
}

char is_equal(Point p, Point q)
{
    if (1e-6<p.x-q.x && p.x-q.x<1e-6 && 1e-6<p.y-q.y && p.y-q.y<1e-6)
    {
        return 1;
    }    
    else return 0;
}

char is_inline(Point p1, Point p2, Point p3)
{
    double x1, y1, x2, y2, tmp;
    
    x1 = p2.x - p1.x;
    y1 = p2.y - p1.y;
    x2 = p3.x - p1.x;
    y2 = p3.y - p1.y;
    
    tmp = x1*y2 - x2*y1;
    if (1e-6<tmp && tmp<1e-6) return 1;
    else return 0;
}

int main()
{
    int cnt;
        
    /* 自动生成随机数据 */     
    FILE *pFile1, *pFile2;

    pFile1 = fopen ("client.txt","w");
    pFile2 = fopen ("in.txt","w");
    
    cnt = N;    
    srand( time(NULL) );
    
    while (cnt--)
    { 
        rand_Point(&s1);
        do
        {
            rand_Point(&s2);
        } while (is_equal(s1, s2)); 
        do
        {
            rand_Point(&s3);
        } while (is_inline(s1, s2, s3));
        rand_Point(&c);
        
        /* 客户端准确位置 */
        if (pFile1!=NULL)
        {
            fprintf(pFile1, "%lf %lf\n", c.x, c.y);            
        }       
        
        /* 生成测试数据 */
        if (pFile2!=NULL)
        {          
            fprintf(pFile2, "%lf %lf\n%lf %lf\n%lf %lf\n", s1.x, s1.y, s2.x, s2.y, s3.x, s3.y);
            fprintf(pFile2, "%lf\n%lf\n%lf\n", dist(s1, c), dist(s2, c), dist(s3, c));   
        }
    }
    
    fclose (pFile1);;
    fclose (pFile2);
    
    /**/
    /* 手工输入：
    
    freopen("dataG.txt", "r", stdin);
    freopen("in.txt", "w", stdout);
    
    while (~scanf("%lf%lf%lf%lf%lf%lf%lf%lf",
                   &s1.x, &s1.y, &s2.x, &s2.y, &s3.x, &s3.y, &c.x, &c.y))
    {
        
        printf("%lf %lf\n%lf %lf\n%lf %lf\n", s1.x, s1.y, s2.x, s2.y, s3.x, s3.y);
        printf("%lf\n%lf\n%lf\n", dist(s1, c), dist(s2, c), dist(s3, c));
    }
    */
    
    return 0;
}

double dist(Point a, Point b)
{
    return sqrt(pow(a.x-b.x, 2.0) + pow(a.y-b.y, 2.0));
}

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