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1、初学C语言常用简单程序代码素数的筛选#i nclude <stdio.h>#in elude <math.h>#defi ne N 1000int main (i nt argc, char* argv)int i,j, num N;for(i=0;i<N;i+)nu mi二i+1;for(i=1;i<(i nt)sqrt(double)N);i+) if(n umi)for(j=i+1;j<N;j+)if(nu mj)if(nu mj% numi=0)nu mj=O;for(i=1;i<N;i+)if(n umi)printf(" %
2、d",numi); return 0;输出时分秒#in clude <stdio.h>mai n()int x,s,t,d;sea nf("%d"，& x);s=x%60;t=(x/60)%60;d=(x/60)/60;prin tf("%d时 %d分 %秒 ",d,t,s);三个数的交换#i nclude <stdio.h>void mai n()int a,b,c,t;sca nf("%d%d%d", &a,&b,&c);prin tf("The orig
3、 inal nu mber:a=%d,b=%d,c=%dn",a,b,c);t=a,a=b,b=t;t=a,a=c,c=t;prin tf("after swap:a=%d,b=%d,c=%d",a,b,c);switch语句的运用#i nclude <stdio.h>mai n()int a,m;prin tf("please in put a nu mber:");sca nf("%d", &a);switch(a/10)case 10:case 9: m=5; break;case 8: m=4;
4、break;case 7:m=3; break;case 6:m=2; break; default:m=1;prin tf("m=%d",m);判断奇数和偶数#i nclude <stdio.h>mai n()int x;prin tf("Please in put a nu mber:"); sca nf("%d"，& x);if(x%2=0)prin tf("this is a oush u!");elseprin tf("this is a jishu!");小写改大
5、写，若是大写则不变in clude <stdio.h>mai n()char c1,c2;prin tf("I nput a letter n");sca nf("%c", &c1);c2=('a'<=c1 &&c1<二'z')?(c1-'a'+'A'):c1; prin tf("%c",c2);getchar();return 0;输入一个数，输出这个数是几位数#i nclude <stdio.h>mai n(
6、)int x,n;prin tf("please in put a nu mber:");sca nf("%d"，& x);n=0;while(x!=O)x=x/10;n+;prin tf("%d", n);输入一个数，判断它是几位数，然后逆序输出#in clude<stdio.h>int mai n()int num;int len 二 0;int temp =0;prin tf("Please in put a nu mber:n");sca nf("%d",&n
7、u m);while( num % 10)!=0)temp = temp*10+( nu m%10);len+;num = nu m/10;prin tf("le ngth = %dn",le n);prin tf("Reverse is %d", temp);打印水仙花数#i nclude <stdio.h>mai n()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)prin tf("%5d",x
8、);prin tf("n");判断闰年#i nclude "stdio.h"mai n()int k,flag ,n=0;for(k=1980;kv=2880;k+)-S 齐0_4OU&LUCLTOP4SV pnous 矣瘁u 4|钱 宀_En5p%HLUns=)匕 £d._*4+LunsHLUns VJL(0+H-LOLHvo.ll)04HJLHHLUns-i-rTuuns 4£OU&LUCLTOP4SV pnousIMB5厂+66.|<10+00丄钱宀厂 Uct3u 一d宀 宀(ucgd(OXOL%U)七 +
9、UOP9%=)七£d ) (曇)4一&只00寸兰-(0|!.00厂>|)0303(0只寸>|6舉int n ,i,fz,fm;s=0;fz=2;fm=1;printf("Enter n:");sca nf("%d",&n);for(i=1;i< 二n ;i+)t=(1.0*fz)/fm;s=s+t;fz=fz+fm;fm=fz-fm;prin tf("s=%fn",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*/#i nc
10、lude <stdio.h>mai n()float average,total;int coun ter,score;total=0.0;coun ter=0;printf(”输入成绩,-1表示结束:");sca nf("%d", &score);while(score!=-1) /*用-1表示输入的结束，同时循环输入分数*/total二total+score;coun ter+;printf("输入下一个成绩,-1表示输入结束：”);sca nf("%d",&score);if(co un ter!=0
11、)average二total/co un ter;printf(”全班平均成绩为：%.2fn",average);elseprintf("没有输入成绩n");return 0;求二元一次方程的根#i nclude <stdio.h>#in clude <math.h>mai n()float a=4,b=-40,c=91;float x1,x2;float delta;delta二sqrt(b*b-4.0*a*c);x仁(-b+delta)/(2.0*a);x2=(-b-delta)/(2.0*a);prin tf("x 1=%f
12、 x2=%fn",x1,x2);if语句的运用#i nclude <stdio.h>mai n()int a,b,c,s,w,t;s=w=t=O;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#i nclude <stdio.h>mai n()int yO,mO,dO,y1,m1,d1,age; prin t
13、f("nplease in put birthday (yyyy/mm/dd):"); sea nf("%d/%d/%d "，&yO,&mO,& d0);prin tf("nplease in put curre nt day(yyyy/mm/dd):");sca nf("%d/%d/%d "，& y1, &m1, &d1);if(m1>m0) | (m 1=m0 && d1>=d0) age=y1-y0;elseage=y1-y0-1;p
14、rin tf("age=%d n ”,age);指针变量作为函数参数，实现两数的交换#i nclude <stdio.h>void sswap(i nt *x,i nt *y);mai n()int a=10,b=20;prin tf("before swap:a=%d,b=%dn",a,b); sswap(&a,&b);prin tf("after swap:a=%d,b=%dn",a,b);void sswap(i nt *x,i nt *y)int t;t=*x;*x=*y;*y=t;通过函数调用输出两个实型数
15、中最大的一个#i nclude <stdio.h>float *f(float *px,float *py)if(*px>*py)return px;retur n py;mai n()float x=10.0,y=20.0,*a 二& x,*b=&y;prin tf("*a=%f,*b=%f,max=%fn",*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#i nclude <stdio.h>void Lower2Upper(ch
16、ar *str)char *p=str;while(*p!=0)if(*p<='z'&&*p>='a')*p=*p-32;p+;mai n()char s10="Hello!"int i;Lower2Upper(s); for(i=0;i<10;i+) prin tf("%c",si);计算一个字符在一个字符串中出现的次数#i nclude <stdio.h>int coun t(char ch,char *str)char *p=str;int num=0; while(*p
17、!='0')if(*p+=ch)nu m+;return num;mai n()char ah='a'char s="haowareayou"prin tf("the nu mber is:");prin tf("%dn",cou nt('a',s);删除一维数组中所有相同的数#in clude <stdio.h>void uniq ue(i nt *a,i nt *n)int k=1;int i,m;m=a0;for(i=0;i<* n;i+)if(ai>m)a
18、k+=ai; m=ai;*n 二k;mai n()int a10;int n=10,i;prin tf("i nput a list nu mber:"); for(i=0;i <n ;i+)sea nf("%d", &ai);prin tf("Before delete:n"); for(i=0;i <n ;i+)prin tf("%d",ai);uniq ue(a，&n);prin tf("after delete.' n"); for(i=0;i <
19、;n ;i+)prin tf("%d",ai);prin tf("n");将字符串按字典顺序输出#i nclude <stdio.h>#i nclude <stri ng.h>#defi ne N 5void sort(char *n ame,i nt n);void prn( char *n ame,i nt n);void mai n()char*n ame="Chi na","America","Australia","Fra nce",&quo
20、t;Germa n" sort (n ame,N);prn( name,N);void sort(char *n ame,i nt 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( namek, namej)>0)k=j; if(k!=i) pt=n amei;n amei=n amek;n amek=pt;void prn( char *n ame,i nt n)int i;for(i=0;i <n ;i+)prin tf("%sn", na
21、mei);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#i nclude <stdio.h>#defi ne N 5 #define M 4,int col);void prt(float *s,i nt n o,i nt len); mai n()float aNM=78,99,89,87,67,59,87,77,86,53,59,95,77,88,57,95,78,75,87,95;score(a,N,M);void score(float (*p)M,i nt row,i nt col)int i,j;int passed;for(i=0;i<row;i+)passed=1;for(j=0;j<col;j+)if(pij<60.0)passed=0;if(!passed) prt(pi,i,col);void prt(float *s,i nt n o,i nt len) float *p;prin tf("NO.%d", no); for(p=s;p<s+le n-1;p+) prin tf("%5.1f",*p);prin tf("n");