【精华篇】C语言入门级练习20题(一):

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Practice 1:

输入一个正整数n，求1+2+3+......+n的和。

#include <stdio.h>#include <stdlib.h>int main(){    int i,n,sum;    printf("Enter n:");    scanf("%d",&n);    sum=0;    for(i=1;i<=n;i++)    {        sum=sum+i;    }    printf("Sum of numbers from 1 to %d is %d\n",n,sum);    return 0;}

Practice 2:

输入一个正整数n，求1-1/3+1/5-1/7+......共n项之和。

#include <stdio.h>#include <stdlib.h>int main(void){    int denominator,flag,i,n;    double item,sum;    printf("Enter n:");    scanf("%d",&n);    flag=1;    denominator=1;    sum=0;    for(i=1;i<=n;i++)    {        item=flag*1.0/denominator;        sum=sum+item;        flag=-flag;        denominator=denominator+2;    }    printf("sum=%f\n",sum);    return 0;}

Practice 3:

从键盘输入一个正整数，计算n！。

#include <stdio.h>#include <stdlib.h>int main(void){    int sum=1,i,n;    printf("Enter n:");    scanf("%d",&n);    for(i=n;i>=1;i--)    {        sum=sum*i;    }    printf("sum的值为%d",sum);    return 0;}

practice 4:

简单的猜数游戏。输入你所猜的整数（假定1~100内），与计算机产生的被猜数比较。若相等；显示猜中，显示与被猜数的大小关系。

#include <stdio.h>#include <stdlib.h>int main(void){    int mynumber=38;    int yournumber;    printf("Input your number:");    scanf("%d",&yournumber);    if(yournumber==mynumber)    {        printf("OK!you are right!\n");    }    else        if(yournumber>mynumber)            printf("Sorry!your number is bigger than my number!\n");        else            printf("Sorry!your number is smaller than my number!\n");        return 0;}

practice 5:

输入一个正整数n，再输入n个学生的成绩，计算平均分，并统计不及格成绩的学生人数。

#include <stdio.h>#include <stdlib.h>int main(){    int count,i,n;    double grade,total;    printf("Enter n:");    scanf("%d",&n);    total=0;    count=0;    for(i=1;i<=n;i++){        printf("Enter grade#%d:",i);        scanf("%lf",&grade);        total=total+grade;        if(grade<60){            count++;        }    }    printf("Grade average=%.2f\n",total/n);    printf("Number of failures=%d\n",count);    return 0;}

practice 6:

求解简单的四则运算表达式，输入一个形式如“操作数运算符操作数”的四则运算表达式，输出运算结果。

#include <stdio.h>#include <stdlib.h>int main(){    double value1,value2;    char op;    printf("Type in an expression:");    scanf("%lf%c%lf",&value1,&op,&value2);    if(op=='+')        printf("=%.2f\n",value1+value2);    else if(op=='-')        printf("=%.2f\n",value1-value2);    else if(op=='*')        printf("=%.2f\n",value1*value2);    else if(op=='/')        printf("=%.2f\n",value1/value2);    else printf("Unknown operator\n");    return 0;}

practice:7

输入10个字符，统计其中英文字母、数字字符和其他字符的个数。

#include <stdio.h>#include <stdlib.h>int main(){    int digit,letter,other;    char ch;    int i;    digit=letter=other=0;    printf("Enter 10 characters:");    for(i=1;i<=10;i++)    {        ch=getchar();        if((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z'))            letter++;        else if(ch>='0'&&ch<='9')            digit++;        else other++;    }    printf("letter=%d,digit=%d,other=%d\n",letter,digit,other);    return 0;}

practice 8:

求解简单表达式。输入一个形式如“操作数运算符操作数”的四则运算表达式，输出运算结果，要求使用switch语句编写。

#include <stdio.h>#include <stdlib.h>int main(){    double value1,value2;    char op;    printf("Type in an expression:");    scanf("%lf%c%lf",&value1,&op,&value2);    switch(op){    case '+':        printf("=%.2f\n",value1+value2);        break;    case '-':        printf("=%.2f\n",value1-value2);        break;    case '*':        printf("=%.2f\n",value1*value2);        break;    case '/':        printf("=%.2f\n",value1/value2);        break;    default:        printf("Unknown operation\n");        break;    }    return 0;}

practice 9:

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