近100个C语言基础算法案例（初级篇）

下面这些C语言基础算法案例都是经过测试和验证过了的，欢迎各位使用。

本文是该系列的第一篇，都是一些相对初级的算法，很适合刚开始学C语言的同学。

转自：http://www.codeceo.com/article/100-c-programming-code.html

1、C语言打印一条语句

源代码：

/* C Program to print a sentence. */#include <stdio.h>int main(){   printf("C Programming"); /* printf() prints the content inside quotation */   return 0;}

输出：

C Programming

2、C语言打印用户输入的一个整数

源代码：

#include <stdio.h>int main(){    int num;    printf("Enter a integer: ");      scanf("%d",&num);  /* Storing a integer entered by user in variable num */    printf("You entered: %d",num);    return 0;}

输出：

Enter a integer: 25You entered: 25

3、C语言实现两个整数相加

源代码：

/*C programming source code to add and display the sum of two integers entered by user */#include <stdio.h>int main( ){    int num1, num2, sum;    printf("Enter two integers: ");    scanf("%d %d",&num1,&num2); /* Stores the two integer entered by user in variable num1 and num2 */    sum=num1+num2;      /* Performs addition and stores it in variable sum */    printf("Sum: %d",sum);  /* Displays sum */    return 0;}

输出：

Enter two integers: 1211Sum: 23

4、C语言实现两个小数相乘

源代码：

/*C program to multiply and display the product of two floating point numbers entered by user. */#include <stdio.h>int main( ){    float num1, num2, product;    printf("Enter two numbers: ");    scanf("%f %f",&num1,&num2);        /* Stores the two floating point numbers entered by user in variable num1 and num2 respectively */    product = num1*num2;  /* Performs multiplication and stores it */    printf("Product: %f",product);    return 0;}

输出：

Enter two numbers: 2.41.1Product: 2.640000

5、C语言查找字符的ASCII值

源代码：

/* Source code to find ASCII value of a character entered by user */#include <stdio.h>int main(){    char c;    printf("Enter a character: ");    scanf("%c",&c);        /* Takes a character from user */    printf("ASCII value of %c = %d",c,c);    return 0;}

输出：

Enter a character: GASCII value of G = 71

6、C语言根据用户输入的整数做商和余数

源代码：

/* C Program to compute remainder and quotient  */#include <stdio.h>int main(){    int dividend, divisor, quotient, remainder;    printf("Enter dividend: ");    scanf("%d",&dividend);    printf("Enter divisor: ");    scanf("%d",&divisor);    quotient=dividend/divisor;           /*  Computes quotient */    remainder=dividend%divisor;          /* Computes remainder */    printf("Quotient = %d\n",quotient);    printf("Remainder = %d",remainder);    return 0;}

输出：

Enter dividend: 25Enter divisor: 4Quotient = 6Remainder = 1

7、C语言获取整型、单精度浮点型、双精度浮点型和字符型的长度

基本语法是：

temp = sizeof(operand);/* Here, temp is a variable of type integer,i.e, sizeof() operator    returns integer value. */

源代码：

/* This program computes the size of variable using sizeof operator.*/#include <stdio.h>int main(){    int a;    float b;    double c;    char d;    printf("Size of int: %d bytes\n",sizeof(a));    printf("Size of float: %d bytes\n",sizeof(b));    printf("Size of double: %d bytes\n",sizeof(c));    printf("Size of char: %d byte\n",sizeof(d));    return 0;}

输出：

Size of int: 4 bytesSize of float: 4 bytesSize of double: 8 bytesSize of char: 1 byte

注：可能会由于系统的不同出来的结果也不尽相同。

8、C语言获取关键字long的长度范围

源代码：

#include <stdio.h>int main(){    int a;    long int b;                /* int is optional. */    long long int c;            /* int is optional. */    printf("Size of int = %d bytes\n",sizeof(a));    printf("Size of long int = %ld bytes\n",sizeof(b));    printf("Size of long long int = %ld bytes",sizeof(c));    return 0;}

输出：

Size of int = 4 bytesSize of long int = 4 bytesSize of long long int = 8 bytes

9、C语言交换数值

源代码：

#include <stdio.h>int main(){      float a, b, temp;      printf("Enter value of a: ");      scanf("%f",&a);      printf("Enter value of b: ");      scanf("%f",&b);      temp = a;    /* Value of a is stored in variable temp */      a = b;       /* Value of b is stored in variable a */      b = temp;    /* Value of temp(which contains initial value of a) is stored in variable b*/      printf("\nAfter swapping, value of a = %.2f\n", a);      printf("After swapping, value of b = %.2f", b);      return 0;}

输出：

Enter value of a: 1.20Enter value of b: 2.45After swapping, value of a = 2.45After swapping, value of b = 1.2

10、C语言检查数值是奇数还是偶数

源代码：

/*C program to check whether a number entered by user is even or odd. */#include <stdio.h>int main(){      int num;      printf("Enter an integer you want to check: ");      scanf("%d",&num);      if((num%2)==0)      /* Checking whether remainder is 0 or not. */           printf("%d is even.",num);      else           printf("%d is odd.",num);      return 0;}

输出1：

Enter an integer you want to check: 2525 is odd.

输出2：

Enter an integer you want to check: 1212 is even.

也可以用条件运算符解决：

/* C program to check whether an integer is odd or even using conditional operator */#include <stdio.h>int main(){    int num;    printf("Enter an integer you want to check: ");    scanf("%d",&num);    ((num%2)==0) ? printf("%d is even.",num) : printf("%d is odd.",num);    return 0;}

11、C语言检查是元音还是辅音

源代码：

#include <stdio.h>int main(){  char c;  printf("Enter an alphabet: ");  scanf("%c",&c);  if(c=='a'||c=='A'||c=='e'||c=='E'||c=='i'||c=='I'||c=='o'||c=='O'||c=='u'||c=='U')       printf("%c is a vowel.",c);  else       printf("%c is a consonant.",c);  return 0;}

输出1：

Enter an alphabet: ii is a vowel.

输出2：

Enter an alphabet: GG is a consonant.

也可以用条件运算符解决

/* C program to check whether a character is vowel or consonant using conditional operator */#include <stdio.h>int main(){ char c; printf("Enter an alphabet: "); scanf("%c",&c); (c=='a'||c=='A'||c=='e'||c=='E'||c=='i'||c=='I'||c=='o'||c=='O'||c=='u'||c=='U') ? printf("%c is a vowel.",c) : printf("%c is a consonant.",c);  return 0;}

输出结果和上面的程序相同。

12、C语言实现从三个数值中查找最大值

实现1：

/* C program to find largest number using if statement only */#include <stdio.h>int main(){      float a, b, c;      printf("Enter three numbers: ");      scanf("%f %f %f", &a, &b, &c);      if(a>=b && a>=c)         printf("Largest number = %.2f", a);      if(b>=a && b>=c)         printf("Largest number = %.2f", b);      if(c>=a && c>=b)         printf("Largest number = %.2f", c);      return 0;}

实现2：

/* C program to find largest number using if...else statement */#include <stdio.h>int main(){      float a, b, c;      printf("Enter three numbers: ");      scanf("%f %f %f", &a, &b, &c);      if (a>=b)      {          if(a>=c)            printf("Largest number = %.2f",a);          else            printf("Largest number = %.2f",c);      }      else      {          if(b>=c)            printf("Largest number = %.2f",b);          else            printf("Largest number = %.2f",c);      }      return 0;}

实现3：

/* C Program to find largest number using nested if...else statement */#include <stdio.h>int main(){      float a, b, c;      printf("Enter three numbers: ");      scanf("%f %f %f", &a, &b, &c);      if(a>=b && a>=c)         printf("Largest number = %.2f", a);      else if(b>=a && b>=c)         printf("Largest number = %.2f", b);      else         printf("Largest number = %.2f", c);      return 0;}

输出结果相同：

Enter three numbers: 12.213.45210.193Largest number = 13.45

13、C语言解一元二次方程

源代码：

/* Program to find roots of a quadratic equation when coefficients are entered by user. *//* Library function sqrt() computes the square root. */#include <stdio.h>#include <math.h> /* This is needed to use sqrt() function.*/int main(){  float a, b, c, determinant, r1,r2, real, imag;  printf("Enter coefficients a, b and c: ");  scanf("%f%f%f",&a,&b,&c);  determinant=b*b-4*a*c;  if (determinant>0)  {      r1= (-b+sqrt(determinant))/(2*a);      r2= (-b-sqrt(determinant))/(2*a);      printf("Roots are: %.2f and %.2f",r1 , r2);  }  else if (determinant==0)  {    r1 = r2 = -b/(2*a);    printf("Roots are: %.2f and %.2f", r1, r2);  }  else  {    real= -b/(2*a);    imag = sqrt(-determinant)/(2*a);    printf("Roots are: %.2f+%.2fi and %.2f-%.2fi", real, imag, real, imag);  }  return 0;}

输出1：

Enter coefficients a, b and c: 2.345.6Roots are: -0.87+1.30i and -0.87-1.30i

输出2：

Enter coefficients a, b and c: 410Roots are: 0.00 and -0.25

14、C语言检查是否是闰年

源代码：

/* C program to check whether a year is leap year or not using if else statement.*/#include <stdio.h>int main(){      int year;      printf("Enter a year: ");      scanf("%d",&year);      if(year%4 == 0)      {          if( year%100 == 0) /* Checking for a century year */          {              if ( year%400 == 0)                 printf("%d is a leap year.", year);              else                 printf("%d is not a leap year.", year);          }          else             printf("%d is a leap year.", year );      }      else         printf("%d is not a leap year.", year);      return 0;}

输出1：

Enter year: 20002000 is a leap year.

输出2：

Enter year: 19001900 is not a leap year.

输出3：

Enter year: 20122012 is a leap year.

15、C语言检查一个数是正数、负数还是零

源代码：

#include <stdio.h>int main(){    float num;    printf("Enter a number: ");    scanf("%f",&num);    if (num<=0)    {        if (num==0)          printf("You entered zero.");        else          printf("%.2f is negative.",num);    }    else      printf("%.2f is positive.",num);    return 0;}

也可以使用if-else语句

/* C programming code to check whether a number is negative or positive or zero using nested if...else statement. */#include <stdio.h>int main(){    float num;    printf("Enter a number: ");    scanf("%f",&num);    if (num<0)      /* Checking whether num is less than 0*/      printf("%.2f is negative.",num);    else if (num>0)   /* Checking whether num is greater than zero*/      printf("%.2f is positive.",num);    else      printf("You entered zero.");    return 0;}

输出1：

Enter a number: 12.312.30 is positive.

输出2：

Enter a number: -12.3-12.30 is negative.

输出3：

Enter a number: 0You entered zero.

16、C语言检查某字符串是不是字母

源代码：

/* C programming code to check whether a character is alphabet or not.*/#include <stdio.h>int main(){    char c;    printf("Enter a character: ");    scanf("%c",&c);    if( (c>='a'&& c<='z') || (c>='A' && c<='Z'))       printf("%c is an alphabet.",c);    else       printf("%c is not an alphabet.",c);    return 0;}

输出1：

Enter a character: ** is not an alphabet

输出2：

Enter a character: KK is an alphabet

17、C语言计算自然数的和

源代码：

/* This program is solved using while loop. */#include <stdio.h>int main(){    int n, count, sum=0;    printf("Enter an integer: ");    scanf("%d",&n);    count=1;    while(count<=n)       /* while loop terminates if count>n */    {        sum+=count;       /* sum=sum+count */        ++count;    }    printf("Sum = %d",sum);    return 0;}

也可以使用for循环语句

/* This program is solve using for loop. */#include <stdio.h>int main(){    int n, count, sum=0;    printf("Enter an integer: ");    scanf("%d",&n);    for(count=1;count<=n;++count)  /* for loop terminates if count>n */    {        sum+=count;                /* sum=sum+count */    }    printf("Sum = %d",sum);    return 0;}

输出：

Enter an integer: 100Sum = 5050

也可以通过if-else语句

/* This program displays error message when user enters negative number or 0 and displays the sum of natural numbers if user enters positive number. */#include <stdio.h>int main(){    int n, count, sum=0;    printf("Enter an integer: ");    scanf("%d",&n);    if ( n<= 0)        printf("Error!!!!");    else    {       for(count=1;count<=n;++count)  /* for loop terminates if count>n */       {           sum+=count;                    /* sum=sum+count */       }       printf("Sum = %d",sum);    }    return 0;}

18、C语言计算阶乘

对于任意正数n，阶乘指的是：

factorial = 1*2*3*4....n

如果数值是负数，那么阶乘就不存在。并且我们规定，0的阶乘就是1。

源代码：

/* C program to display factorial of an integer if user enters non-negative integer. */#include <stdio.h>int main(){    int n, count;    unsigned long long int factorial=1;             printf("Enter an integer: ");    scanf("%d",&n);    if ( n< 0)        printf("Error!!! Factorial of negative number doesn't exist.");    else    {       for(count=1;count<=n;++count)    /* for loop terminates if count>n */       {          factorial*=count;              /* factorial=factorial*count */       }    printf("Factorial = %lu",factorial);    }    return 0;}

输出1：

Enter an integer: -5Error!!! Factorial of negative number doesn't exist.

输出2：

Enter an integer: 10Factorial = 3628800