近100個C語言基礎算法案例（初級篇）
下面這些C語言基礎算法案例都是經過測試和驗證過了的，歡迎各位使用。
本文是該系列的第一篇，都是一些相對初級的算法，很適合剛開始學C語言的同學。
1、C語言打印一條語句
源代碼：
/ C Program to print a sentence. /include <stdio.h>
int main() { printf("C Programming"); / printf() prints the content inside quotation / return 0; }</pre>
輸出：
C Programming2、C語言打印用戶輸入的一個整數
源代碼：
#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; }輸出：
Enter a integer: 25 You entered: 253、C語言實現兩個整數相加
源代碼：
/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;}</pre>
輸出：
Enter two integers: 12 11 Sum: 234、C語言實現兩個小數相乘
源代碼：
/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 = num1num2; / Performs multiplication and stores it */ printf("Product: %f",product); return 0; }</pre>
輸出：
Enter two numbers: 2.4 1.1 Product: 2.6400005、C語言查找字符的ASCII值
源代碼：
/ 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; }</pre>
輸出：
Enter a character: G ASCII value of G = 716、C語言根據用戶輸入的整數做商和余數
源代碼：
/ C Program to compute remainder and quotient /include <stdio.h>
int main(){ int dividend, divisor, quotient, remainder; printf("Enter dividend: "); scanf("%d",÷nd); 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; }</pre>
輸出：
Enter dividend: 25 Enter divisor: 4 Quotient = 6 Remainder = 17、C語言獲取整型、單精度浮點型、雙精度浮點型和字符型的長度
基本語法是：
temp = sizeof(operand); /* Here, temp is a variable of type integer,i.e, sizeof() operator returns integer value. */源代碼：
/ 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; }</pre>
輸出：
Size of int: 4 bytes Size of float: 4 bytes Size of double: 8 bytes Size of char: 1 byte注：可能會由于系統的不同出來的結果也不盡相同。
8、C語言獲取關鍵字long的長度范圍
源代碼：
#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; }輸出：
Size of int = 4 bytes Size of long int = 4 bytes Size of long long int = 8 bytes9、C語言交換數值
源代碼：
#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; }輸出：
Enter value of a: 1.20 Enter value of b: 2.45After swapping, value of a = 2.45 After swapping, value of b = 1.2</pre>
10、C語言檢查數值是奇數還是偶數
源代碼：
/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; }</pre>
輸出1：
Enter an integer you want to check: 25 25 is odd.輸出2：
Enter an integer you want to check: 12 12 is even.也可以用條件運算符解決：
/ 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; }</pre>
11、C語言檢查是元音還是輔音
源代碼：
#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; }輸出1：
Enter an alphabet: i i is a vowel.輸出2：
Enter an alphabet: G G is a consonant.也可以用條件運算符解決
/ 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; }</pre>
輸出結果和上面的程序相同。
12、C語言實現從三個數值中查找最大值
實現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; }</pre>
實現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; }</pre>
實現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; }</pre>
輸出結果相同：
Enter three numbers: 12.2 13.452 10.193 Largest number = 13.4513、C語言解一元二次方程
源代碼：
/ 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=bb-4ac; if (determinant>0) { r1= (-b+sqrt(determinant))/(2a); r2= (-b-sqrt(determinant))/(2a); printf("Roots are: %.2f and %.2f",r1 , r2); } else if (determinant==0) { r1 = r2 = -b/(2a); printf("Roots are: %.2f and %.2f", r1, r2); } else { real= -b/(2a); imag = sqrt(-determinant)/(2a); printf("Roots are: %.2f+%.2fi and %.2f-%.2fi", real, imag, real, imag); } return 0; }</pre>
輸出1：
Enter coefficients a, b and c: 2.3 4 5.6 Roots are: -0.87+1.30i and -0.87-1.30i輸出2：
Enter coefficients a, b and c: 4 1 0 Roots are: 0.00 and -0.2514、C語言檢查是否是閏年
源代碼：
/ 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; }</pre>
輸出1：
Enter year: 2000 2000 is a leap year.輸出2：
Enter year: 1900 1900 is not a leap year.輸出3：
Enter year: 2012 2012 is a leap year.15、C語言檢查一個數是正數、負數還是零
源代碼：
#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語句
/ 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; }</pre>
輸出1：
Enter a number: 12.3 12.30 is positive.輸出2：
Enter a number: -12.3 -12.30 is negative.輸出3：
Enter a number: 0 You entered zero.16、C語言檢查某字符串是不是字母
源代碼：
/ 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; }</pre>
輸出1：
Enter a character: *
- is not an alphabet</pre>
輸出2：
Enter a character: K K is an alphabet
17、C語言計算自然數的和
源代碼：
/ 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; }</pre>
也可以使用for循環語句
/ 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; }</pre>
輸出：
Enter an integer: 100 Sum = 5050也可以通過if-else語句
/ 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; }</pre>
18、C語言計算階乘
對于任意正數n，階乘指的是：
factorial = 1*2*3*4....n如果數值是負數，那么階乘就不存在。并且我們規定，0的階乘就是1。
源代碼：
/ 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=factorialcount / } printf("Factorial = %lu",factorial); } return 0; }</pre>輸出1：
Enter an integer: -5 Error!!! Factorial of negative number doesn't exist.輸出2：
Enter an integer: 10 Factorial = 3628800先介紹到這里，下一篇將分享更多的C語言基礎算法
譯文鏈接：http://www.codeceo.com/article/100-c-programming-code.html
英文原文：C Programming Examples
翻譯作者：碼農網 – 小峰