杂乱整理

One day 回顾C++语法（杂乱的）

1.输出格式

	int s = 10;
	printf("%d\n",s); 
	
	int a,b;
	scanf("%d%d",&a,&b);
	printf("%d",a+b);

2.字符串操作

	char str1[20];
	char str2[5][20];
	gets(str1);		//输入字符串 
	for(int i = 0;i<3;i++){
		gets(str2[i]);
	} 
	puts(str1);		//输出字符串 
	for(int i = 0;i<3;i++){
		puts(str2[i]);
	} 

3.定义别名

#include<stdio.h>
typedef long long LL; 
int main(){
	LL a = 12346797987;
	printf("%lld",a); 
	return 0;
} 

4.符号常量和const常量

#include<stdio.h>
 
//符号常量和const常量 
#define PI 3.14
const double pi = 3.14;
#define ADD(a,b) ((a+b)) 
int main(){
	int num = 1234567891LL;
	printf("%d\n",num);
	char a[25] = "I Love You";
	char c[25] = "Me Too";
	printf("%s\n%s\n",a,c);
	printf("%.

5.向上向下取整

#include<stdio.h>
#include<cmath>
int main(){
	double  a = 2.5,v = -2.5;
	printf("%.0f\t%.0f\n",floor(a),ceil(a));
	printf("%.0f\t%.0f\n",floor(v),ceil(v));
	//返回double类型 
	double c = round(3.55);
	printf("%d\n",int(c));
	return 0;
} 

6.结构体

#include<stdio.h>
struct Point{
	int x,y;
	Point(){}
	Point(int _x,int _y){
		x = _x;
		y = _y;
	} 
	//或者 Point(int _x,int_y):x(_x),y(_y){} 
} pt[10];
int main(){
	int num = 0;
	for(int i = 1;i<=3;i++)
		for(int j = 1;j<=3;j++){
			pt[num++] = Point(i,j);
		}
	for(int i = 0;i<num;i++){
		printf("%d,%d\n",pt[i].x,pt[i].y);
	}
	//指针调用 p->x,p->y或者(*p).x 
	return 0;
} 

7.浮点数比较

#include<stdio.h>
#include<math.h>
const double eps = 1e-8;
//等于 
#define Equ(a,b) ((fabs((a)-(b)))<(eps))
//小于
#define Less(a,b) (((a)-(b))<(-eps))
//大于
#define More(a,b) (((a)-(b))>(eps))
//大于等于
#define MoreEqu(a,b) (((a)-(b))>(-eps))
//小于等于 
#define MoreEqu(a,b) (((a)-(b))<(eps))

const double PI = acos(-1.0 );
int main(){
	double db = 1.23;
	if(Equ(db,1.23)){
		printf("true");
	}else{
		printf("false");
	}
	return 0;
} 

2019.12.23