初学C语言常用简单程序代码素数的筛选#include <stdio.h>#include <math.h>#define N 1000int main(int argc, char* argv[]){int i,j,num[N];for(i=0;i<N;i++)num[i]=i+1;for(i=1;i<(int)sqrt((double)N);i++){if(num[i]){for(j=i+1;j<N;j++){if(num[j])if(num[j]%num[i]==0)num[j]=0;}}}for(i=1;i<N;i++)if(num[i])printf(" %d",num[i]);return 0;}输出时分秒#include <stdio.h>main(){int x,s,t,d;scanf("%d",&x);s=x%60;t=(x/60)%60;d=(x/60)/60;printf("%d时%d分%d秒",d,t,s);}三个数的交换#include <stdio.h>void main(){int a,b,c,t;scanf("%d%d%d",&a,&b,&c);printf("The original number:a=%d,b=%d,c=%d\n",a,b,c); t=a,a=b,b=t;t=a,a=c,c=t;printf("after swap:a=%d,b=%d,c=%d",a,b,c);}switch语句的运用#include <stdio.h>main(){int a,m;printf("please input a number:");scanf("%d",&a);switch(a/10){case 10:case 9: m=5; break;case 8: m=4; break;case 7:m=3; break;case 6:m=2; break;default:m=1;}printf("m=%d",m);}判断奇数和偶数#include <stdio.h>main(){int x;printf("Please input a number: ");scanf("%d",&x);if(x%2==0)printf("this is a oushu!");elseprintf("this is a jishu!");}小写改大写，若是大写则不变include <stdio.h>main(){char c1,c2;printf("Input a letter\n");scanf("%c",&c1);c2=('a'<=c1&&c1<='z')?(c1-'a'+'A'):c1; printf("%c",c2);getchar();return 0;}输入一个数，输出这个数是几位数#include <stdio.h>main(){int x,n;printf("please input a number:");scanf("%d",&x);n=0;while(x!=0){x=x/10;n++;}printf("%d",n);}输入一个数，判断它是几位数，然后逆序输出#include<stdio.h>int main(){int num;int len = 0;int temp =0;printf("Please input a number:\n"); scanf("%d",&num);while((num % 10)!=0){temp = temp*10+(num%10);len++;num = num/10;}printf("length = %d\n",len);printf("Reverse is %d", temp); }打印水仙花数#include <stdio.h>main(){int x, a,b,c;for(x=100;x<=999;x++){a=x%10;b=(x/10)%10;c=x/100;if(x==a*a*a+b*b*b+c*c*c){printf("%5d",x);}}printf("\n");}判断闰年#include "stdio.h"main(){int k,flag,n=0;for(k=1980;k<=2880;k++){flag=(k%4==0)&&(k%100!=0)||(k%400==0);if(flag){ printf("%5d",k);n++;if(n%10==0)printf("\n");}}printf("\n");}求1-3+5-7...-99+101的值#include <stdio.h>main(){int sum,i,t;sum=1;t=1;for(i=3;i<=101;i=i+2){t=-t;sum=sum+t*i;}printf("sum=%d",sum);}求前n项和#include <stdio.h>main(){float s,t;int n,i,fz,fm;s=0;fz=2;fm=1;printf("Enter n:");scanf("%d",&n);for(i=1;i<=n;i++){t=(1.0*fz)/fm;s=s+t;fz=fz+fm;fm=fz-fm;}printf("s=%f\n",s);}开发一个程序求全班学生某门课的平均成绩，要求程序每次运行时班级人数可为任意/*用标记值来指示数据输入的结束*/#include <stdio.h>main(){float average,total;int counter,score;total=0.0;counter=0;printf("输入成绩,-1表示结束:");scanf("%d",&score);while(score!=-1) /*用-1表示输入的结束,同时循环输入分数*/{total=total+score;counter++;printf("输入下一个成绩,-1表示输入结束:");scanf("%d",&score);}if(counter!=0){average=total/counter;printf("全班平均成绩为：%.2f\n",average);}elseprintf("没有输入成绩\n");return 0;}求二元一次方程的根#include <stdio.h>#include <math.h>main(){float a=4,b=-40,c=91;float x1,x2;float delta;delta=sqrt(b*b-4.0*a*c);x1=(-b+delta)/(2.0*a);x2=(-b-delta)/(2.0*a);printf("x1=%f x2=%f\n",x1,x2);}if语句的运用#include <stdio.h>main(){int a,b,c,s,w,t;s=w=t=0;a=-1;b=c=3;if(c>0)s=a+b;if(a<=0){if(b>0)if(c<=0)w=a-b;}elseif(c>0)w=a-b;elset=c;printf("s=%d, w=%d,t=%d",s,w,t); }输入学生的生日，输出他的实足年龄#include <stdio.h>main(){int y0,m0,d0,y1,m1,d1,age;printf("\nplease input birthday (yyyy/mm/dd):");scanf("%d/%d/%d ",&y0,&m0,&d0);printf("\nplease input current day(yyyy/mm/dd):");scanf("%d/%d/%d ",&y1,&m1,&d1);if((m1>m0) || (m1=m0 && d1>=d0))age=y1-y0;elseage=y1-y0-1;printf("age=%d \n",age);}指针变量作为函数参数，实现两数的交换#include <stdio.h>void sswap(int *x,int *y);main(){int a=10,b=20;printf("before swap:a=%d,b=%d\n",a,b);sswap(&a,&b);printf("after swap:a=%d,b=%d\n",a,b);}void sswap(int *x,int *y){int t;t=*x;*x=*y;*y=t;}通过函数调用输出两个实型数中最大的一个#include <stdio.h>float *f(float *px,float *py){if(*px>*py)return px;return py;}main(){float x=10.0,y=20.0,*a=&x,*b=&y;printf("*a=%f,*b=%f,max=%f\n",*a,*b,*f(a,b));}计算并输出一个数组中所有元素的和，最大值，最小值，值为奇数的元素个数编写一个函数，将一个字符串中的字符全部转成大写#include <stdio.h>void Lower2Upper(char *str){char *p=str;while(*p!=0){if(*p<='z'&&*p>='a')*p=*p-32;p++;}}main(){char s[10]="Hello!";int i;Lower2Upper(s);for(i=0;i<10;i++)printf("%c",s[i]);}计算一个字符在一个字符串中出现的次数#include <stdio.h>int count(char ch,char *str){char *p=str;int num=0;while(*p!='\0')if(*p++==ch)num++;return num;}main(){char ah='a';char s[]="haowareayou";printf("the number is:");printf("%d\n",count('a',s));}删除一维数组中所有相同的数#include <stdio.h>void unique(int *a,int *n){int k=1;int i,m;m=a[0];for(i=0;i<*n;i++){if(a[i]>m){a[k++]=a[i];m=a[i];}}*n=k;}main(){int a[10];int n=10,i;printf("input a list number:");for(i=0;i<n;i++)scanf("%d",&a[i]);printf("Before delete:...\n");for(i=0;i<n;i++)printf("%d",a[i]);unique(a,&n);printf("after delete....\n");for(i=0;i<n;i++)printf("%d",a[i]);printf("\n");}将字符串按字典顺序输出#include <stdio.h>#include <string.h>#define N 5void sort(char *name[],int n);void prn(char *name[],int n);void main(){char*name[]={"China","America","Australia","France","German"};sort(name,N);prn(name,N);}void sort(char *name[],int n){char *pt;int i,j,k;for(i=0;i<n-1;i++){k=i;for(j=i+1;j<n;j++)if(strcmp(name[k],name[j])>0)k=j;if(k!=i){pt=name[i];name[i]=name[k];name[k]=pt;}}}void prn(char *name[],int n){int i;for(i=0;i<n;i++)printf("%s\n",name[i]);}有n个学生，每个学生考m门课程，要求编一程序，能检查n个学生有无不及格的课程，如果有某一学生有一门或一门以上课程不及格，就输出该学生的号码和其全部成绩#include <stdio.h>#define N 5#define M 4,int col);void prt(float *s,int no,int len);main(){floata[N][M]={{78,99,89,87},{67,59,87,77},{86,53,59,95},{77,88,5 7,95},{78,75,87,95}};score(a,N,M);}void score(float (*p)[M],int row,int col){int i,j;int passed;for(i=0;i<row;i++){passed=1;for(j=0;j<col;j++)if(p[i][j]<60.0)passed=0;if(!passed)prt(p[i],i,col);}}void prt(float *s,int no,int len) {float *p;printf("NO.%d",no);for(p=s;p<s+len-1;p++)printf("%5.1f",*p);printf("\n");}。