#include<stdio.h>
int a[100][100];
int main(){
    
    
	int n,i,j,sum=1;
	scanf("%d",&n);
	a[1][1]=1;
	for(i=1,j=1;sum<n*n;)
	//此处sum必须严格小于n^2 否则循环无法结束 
	{
    
    
		while(++j<=n && !a[i][j])a[i][j]=++sum;--j;
		while(++i<=n && !a[i][j])a[i][j]=++sum;--i;
		while(--j>=1 && !a[i][j])a[i][j]=++sum;++j;
		while(--i>=1 && !a[i][j])a[i][j]=++sum;++i;
	}
	for(i=1;i<=n;i++){
    
    
		for(j=1;j<=n;j++){
    
    
			printf("%3d",a[i][j]);
		}
		printf("\n");	
	}
	return 0;
}

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

int main(){
    
    
	double x1,x2,x3,y1,y2,y3;
	scanf("%lf %lf",&x1,&y1);
	scanf("%lf %lf",&x2,&y2);
	scanf("%lf %lf",&x3,&y3);
	double len1,len2,len3;
	len1=sqrt(pow((x2-x1),2)+pow((y2-y1),2));
	len2=sqrt(pow((x3-x2),2)+pow((y3-y2),2));
	len3=sqrt(pow((x3-x1),2)+pow((y3-y1),2));
	
	printf("%.2lf",len1+len2+len3);
	return 0;
}

函数写法

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

double dis(double a,double b,double c,double d){
    
    
	return sqrt(pow((c-a),2)+pow((d-b),2));
}

int main(){
    
    
	double x1,y1,x2,y2,x3,y3,a,b,c;
	scanf("%lf %lf %lf %lf %lf %lf",&x1,&y1,&x2,&y2,&x3,&y3);
	a=dis(x1,y1,x2,y2);
	b=dis(x1,y1,x3,y3);
	c=dis(x2,y2,x3,y3);
	printf("%.2lf\n",a+b+c);
	return 0;
}