# 近100个C语言基础算法案例（初级篇）

jopen 7年前

## 1、C语言打印一条语句

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

`C Programming`

## 2、C语言打印用户输入的一个整数

`#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;  }`

`Enter a integer: 25  You entered: 25`

## 3、C语言实现两个整数相加

`/*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;  }`

`Enter two integers: 12  11  Sum: 23`

## 4、C语言实现两个小数相乘

`/*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;  }`

`Enter two numbers: 2.4  1.1  Product: 2.640000`

## 5、C语言查找字符的ASCII值

`/* 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;  }`

`Enter a character: G  ASCII value of G = 71`

## 6、C语言根据用户输入的整数做商和余数

`/* 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;  }`

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

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

`/* 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;  }`

`Size of int: 4 bytes  Size of float: 4 bytes  Size of double: 8 bytes  Size of char: 1 byte`

## 8、C语言获取关键字long的长度范围

`#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;  }`

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

## 9、C语言交换数值

`#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;  }`

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

## 10、C语言检查数值是奇数还是偶数

`/*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;  }`

`Enter an integer you want to check: 25  25 is odd.`

`Enter an integer you want to check: 12  12 is even.`

`/* 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

`#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;  }`

`Enter an alphabet: i  i is a vowel.`

`Enter an alphabet: G  G is a consonant.`

`/* 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;  }`

## 12、C语言实现从三个数值中查找最大值

`/* 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;  }`

`/* 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;  }`

`/* 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;  }`

`Enter three numbers: 12.2  13.452  10.193  Largest number = 13.45`

## 13、C语言解一元二次方程

`/* 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;  }`

`Enter coefficients a, b and c: 2.3  4  5.6  Roots are: -0.87+1.30i and -0.87-1.30i`

`Enter coefficients a, b and c: 4  1  0  Roots are: 0.00 and -0.25`

## 14、C语言检查是否是闰年

`/* 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;  }`

`Enter year: 2000  2000 is a leap year.`

`Enter year: 1900  1900 is not a leap year.`

`Enter year: 2012  2012 is a leap year.`

## 15、C语言检查一个数是正数、负数还是零

`#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;  }`

`/* 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;  }`

`Enter a number: 12.3  12.30 is positive.`

`Enter a number: -12.3  -12.30 is negative.`

`Enter a number: 0  You entered zero.`

## 16、C语言检查某字符串是不是字母

`/* 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;  }`

`Enter a character: *  * is not an alphabet`

`Enter a character: K  K is an alphabet`

## 17、C语言计算自然数的和

`/* 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;  }`

`/* 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;  }`

`Enter an integer: 100  Sum = 5050`

`/* 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

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

`/* 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;  }`

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

`Enter an integer: 10  Factorial = 3628800`