按月打印天数
编译器 计算元素的 个数
#include <stdio.h>
#include <stdlib.h>
#define MONTHS 12
void main()
{
const int days[] = {31,28,31,30 ,31,30,31,31,30,31,30,31};
int i ;
for ( i = 0; i < sizeof (days)/sizeof(days[0]) ; i++)
{
printf(" months = %d dDAY = %d\n",i+1,days[i]);
}
printf("size of (day ) = %d .size of (day[0]= %d",sizeof (days),sizeof(days[0]));
system("pause");
}
指针加法
#include <stdio.h>
#include <stdlib.h>
#define SIZE 4
main()
{ short dates[SIZE];
short *pti;
short index;
double bills[SIZE];
double *ptf;
pti = dates;
ptf = bills;
printf("%23s %10s \n","short " ,"double");
for ( index = 0; index < SIZE; index ++)
{
printf("%d %10p %10p \n",index,pti+index,ptf+index);
}
system("pause");
}
使用指针符号
#include <stdio.h>
#include <stdlib.h>
#define MONTHS 12
main()
{
int days[] = {31,28,31,30 ,31,30,31,31,30,31,30,31};
int i ;
for ( i = 0; i < MONTHS ; i++)
{
printf(" months = %2d dDAY = %5d\n",i+1,*(days+i));
}
system("pause");
}
对一个元素的 所有元素求和
#include <stdio.h>
#include <stdlib.h>
#define MONTHS 12
int sum (int * , int );
main()
{
int days[] = {31,28,31,30 ,31,30,31,31,30,31,30,31};
long answer;
answer = sum (days,MONTHS);
printf("answer = %d\n",answer);
printf("sizeof days = %d\n",sizeof days);
system("pause");
}
int sum ( int * ar , int n)
{
int i, total = 0;
for ( i = 0; i < n; i++)
{
total += *(ar+i);
}
printf("sizeof %d",sizeof ar );
return total;
}
使用指针参数
‘#include <stdio.h>
#include <stdlib.h>
#define MONTHS 12
int sum (int * , int * );
main()
{
int days[] = {31,28,31,30 ,31,30,31,31,30,31,31,31};
long answer;
answer = sum (days,days+ MONTHS);
printf("answer = %d\n",answer);
printf("sizeof days = %d\n",sizeof days);
system("pause");
}
int sum ( int * ar , int* n)
{
int total = 0;
while (ar < n)
{
total += *ar;
ar++;
}
printf("sizeof %d",sizeof ar );
return total;
}
指针运算的 优先3 级
#include <stdio.h>
#include <stdlib.h>
#define MONTHS 12
int data [2] = { 100, 200};
int moredata[2] = { 300,400};
void main()
{
int *p1, *p2 ,*p3;
p1 = p2 = data;
p3 = moredata;
printf("*p1 = %d *p2 = %d *p3 = %d \n", *p1 ,*p2 ,*p3);
printf("*p1++ = %d *++p2 = %d (*p3)++ = %d \n", *p1++ ,*++p2 ,(*p3)++);
printf("*p1 = %d *p2 = %d *p3 = %d \n", *p1 ,*p2 ,*p3);
system("pause");
}
指针操作
#include <stdio.h>
#include <stdlib.h>
void main()
{
int nrn[5] = {100,200,300,400,500};
int * prt1 ,* prt2 ,* prt3;
prt1 = nrn;
prt2 = nrn+2;
printf (" \n adding an int to a pointer ;|\n");
printf("ptr1 = %p *ptr1 = %d &ptr1 = %p \n",prt1,*prt1,&prt1);
prt3 = prt1 + 4;
printf (" \n adding an int to a pointer ;|\n");
printf("ptr1+4 = %p ptr1+4 = %d *(ptr1+3) = %d \n",prt1 +4 ,*(prt1 +4),*(prt1+3));
prt1++;
printf("\n valuess afrerptr1 ++ \n");
printf("ptr1 = %p *ptr1 = %d &ptr1 = %p \n",prt1,*prt1,&prt1);
prt2 --;
printf("ptr2 = %p *ptr2 = %d &ptr2 = %p \n",prt2,*prt2,&prt2);
--prt1;
++prt2;
printf("\n valuess afrerptr1 ++ \n");
printf("ptr1 = %p *ptr1 = %d ptr2 = %p *ptr2 = %d \n",prt1,*prt1,prt2,*prt2);
printf("\n valuess afrerptr1 ++ \n");
printf("ptr2 = %p ptr1 = %p ptr2 -ptr1 = %d \n",prt2,prt1,prt2-prt1);
printf("\n valuess afrerptr1 ++ \n");
printf("ptr3 = %p *ptr3 = %d ptr3 -2 = %p *(ptr3 -2) = %d \n",prt3,*prt3,prt3-2,*(prt3-2));
system("pause");
}
处理 数组的函数 不使用 return 机制
#include <stdio.h>
#include <stdlib.h>
#define SIZE 5
void show_array (const double * , int );
void mult_array(double *,int ,double);
void main()
{
double dip[SIZE] = {20.0,17.66,8.2,15.3,22.22};
printf("the original dip array \n");
show_array(dip , SIZE);
mult_array(dip, SIZE,2.5);
printf("after\n");
show_array(dip , SIZE);
system("pause");
}
void show_array (const double *ar , int n )
{
int i ;
for ( i = 0; i < n; i++)
{
printf("%8.3f",*(ar+i));
}
putchar('\n');
}
void mult_array(double *ar,int n ,double mult)
{
int i ;
for ( i = 0; i < n; i++)
{
* (ar + i) *= mult;
}
}
指针和多位数组
#include <stdio.h>
#include <stdlib.h>
#define SIZE 5
void main()
{
int zippo [4][2] = {{2,4},{6,8},{1,3},{5,7} };
printf("zippo = %p zippo + 1 = %p \n",zippo,zippo+1 );
printf("zippo[0] = %p zippo[0]+1 = %p, \n",zippo[0] ,zippo[0]+1);
printf("*zippo = %p *zippo +1 = %p, \n",*zippo ,*zippo +1);
printf("zippo[0][0] = %d \n",zippo[0][0] );
printf("*zippo [0] = %d \n",*(*(zippo +0)+1) );
printf("zippo[2][1] = %d \n",zippo[2][1] );
printf(" *(*(zippo+2)+1) = %d \n", *(*(zippo+2)+1) );
system("pause");
}
处理二位数组 的函数
#include <stdio.h>
#include <stdlib.h>
#define ROWS 3
#define COLS 4
void sum_rows(int ar[][COLS] ,int );
void sum_cols(int [] [COLS],int );
int sum2d(int (*ar) [COLS] ,int );
void main()
{
int junk[ROWS][COLS] = {
{2,4,6,8},
{3,5,7,9},
{12,10,8,6}
};
sum_rows(junk,ROWS);
sum_cols(junk,ROWS);
printf ("sum of all elements %d \n ",sum2d(junk,ROWS));
system("pause");
}
void sum_rows(int ar[] [COLS] ,int rows )
{
int r;
int c;
int tot;
for (r = 0; r < rows; r++)
{
tot = 0;
for (c = 0; c < COLS; c++)
{
tot += *(*(ar+r)+c);
}
printf("row %d : sum = %d\n" , r, tot);
}
}
void sum_cols(int ar[] [COLS],int rows )
{
int r;
int c;
int tot;
for (c = 0; c < COLS; c++)
{
tot = 0;
for (r = 0; r < rows; r++)
{
tot += *(*(ar+r)+c);
}
printf("row %d : sum = %d\n" , c, tot);
}
}
int sum2d(int ar[] [COLS] ,int rows)
{
int r;
int c;
int tot = 0;
for (r = 0; r <rows ; r++)
{
for (c = 0; c < COLS;c++)
{
tot += *(*(ar+r)+c);
}
}
return tot;
}
\
边长数组vs 2012编译失败 xcode 编译成功
#include <stdio.h>
#include <stdlib.h>
#define ROWS 3
#define COLS 4
int sum2d(int rows ,int cols,int ar[rows][cols]);
void main()
{
int i ,j;
int rs = 3;
int cs = 10;
int junk[ROWS][COLS] = {
{2,4,6,8},
{3,5,7,9},
{12,10,8,6}
};
int morejunk[ROWS -1][COLS+2] = {
{20,30,40,50,60,70},
{5,6,7,8,9,10},
};
int varr[rs][cs];
for ( i = 0; i < rs; i++)
{
for ( j = 0;j < cs; j++)
{
varr [i][j] = i * j +j;
}
}
printf("3*5 array\n");
printf("sum of all elements = %d \n", sum2d(ROWS,COLS,junk));
printf("2*6 array\n");
printf("sum of all elements = %d \n", sum2d(ROWS-1,COLS+2,morejunk));
printf("3*10 array\n");
printf("sum of all elements = %d \n", sum2d(rs,cs,varr));
system("pause");
}
int sum2d(int rows ,int cols,int ar[rows][cols])
{
int r;
int c;
int tot = 0;
for (r = 0; r <rows ; r++)
{
for (c = 0; c < cols;c++)
{
tot += *(*(ar+r)+c);
}
}
return tot;
}
有趣的常数
#include <stdio.h>
#include <stdlib.h>
#define COLS 4
int sum2d(int (*ar)[COLS] ,int );
int sum (int * ,int );
void main()
{
int total1,total2,total3;
int *pt1;
int (*pt2)[COLS];
pt1 = (int [2]) {10,20};
pt2 = (int [2][COLS]) {{1,2,3,-9},{4,5,6,-8}};
total1=sum (pt1,2);
total2=sum2d (pt2,2);
total3=sum ((int [] ){4,4,4,5,5,5},6);
printf("total1 = %d \n", total1);
printf("total2 = %d \n", total2);
printf("total3 = %d \n", total3);
system("pause");
}
int sum (int *ar,int n)
{
int i;
int total = 0;
for(i =0; i <n ; i++)
{
total+= *(ar+i);
}
return total;
}
int sum2d(int (*ar)[COLS] ,int rows)
{
int r;
int c;
int tot = 0;
for(r =0; r <rows ; r++)
{
for (c = 0; c <COLS;c++)
{
tot += *(*(ar+r)+c);
}
}
return tot;
}
#include <stdio.h>
#include <stdlib.h>
void sign_off (void );
void too_bad (void );
void main()
{
int n ;
atexit (sign_off);
puts("enter an integer");
if (scanf ("%d",&n) != 1)
{
puts("THAT NO integer");
atexit(too_bad);
exit(EXIT_FAILURE);
}
printf("%d is %s \n" ,n ,( n % 2 == 0) ? "even" : "odd");
system("pause");
}
void sign_off()
{
puts (" thus terminates another agnificetnt program from");
puts ("seesaw software ");
}
void too_bad()
{
puts (" seesaw software extends its heartfelt condolences ");
puts (" to you upon the failure of your program ");
}
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