文章来源：10个经典的C语言面试基础算法及代码

算法是一个程序和软件的灵魂，作为一名优秀的程序员，只有对一些基础的算法有着全面的掌握，才会在设计程序和编写代码的过程中显得得心应手。

一、计算Fibonacci数列

Fibonacci数列又称斐波那契数列，又称黄金分割数列，指的是这样一个数列：1、1、2、3、5、8、13、21。

C语言实现的代码如下：

/* Displaying Fibonacci sequence up to nth term where n is entered by user. */
#include <stdio.h>
int main()
{int count, n, t1=0, t2=1, display=0;printf("Enter number of terms: ");scanf("%d",&n);printf("Fibonacci Series: %d+%d+", t1, t2); /* Displaying first two terms */count=2;    /* count=2 because first two terms are already displayed. */while (count<n)  {display=t1+t2;t1=t2;t2=display;++count;printf("%d+",display);}return 0;
}

结果输出：

Enter number of terms: 10
Fibonacci Series: 0+1+1+2+3+5+8+13+21+34+

二、回文检查

源代码：


/* C program to check whether a number is palindrome or not */
#include <stdio.h>
int main()
{int n, reverse=0, rem,temp;printf("Enter an integer: ");scanf("%d", &n);temp=n;while(temp!=0){rem=temp%10;reverse=reverse*10+rem;temp/=10;}  
/* Checking if number entered by user and it's reverse number is equal. */  if(reverse==n)  printf("%d is a palindrome.",n);elseprintf("%d is not a palindrome.",n);return 0;
}

结果输出：


Enter an integer: 12321
12321 is a palindrome.

三、质数检查

注：1既不是质数也不是合数。

源代码：


/* C program to check whether a number is prime or not. */
#include <stdio.h>
int main()
{int n, i, flag=0;printf("Enter a positive integer: ");scanf("%d",&n);for(i=2;i<=n/2;++i){if(n%i==0){flag=1;break;}}if (flag==0)printf("%d is a prime number.",n);elseprintf("%d is not a prime number.",n);return 0;
}

结果输出：


Enter a positive integer: 29
29 is a prime number.

四、打印金字塔和三角形

使用 * 建立三角形


*
* *
* * *
* * * *
* * * * *

源代码：


#include <stdio.h>
int main()
{int i,j,rows;printf("Enter the number of rows: ");scanf("%d",&rows);for(i=1;i<=rows;++i){for(j=1;j<=i;++j){printf("* ");}printf("\n");}return 0;
}

如下图所示使用数字打印半金字塔。

源代码：


#include <stdio.h>
int main()
{int i,j,rows;printf("Enter the number of rows: ");scanf("%d",&rows);for(i=1;i<=rows;++i){for(j=1;j<=i;++j){printf("%d ",j);}printf("\n");}return 0;
}

用 * 打印半金字塔：


* * * * *
* * * *
* * * 
* *
*

源代码：


#include <stdio.h>
int main()
{int i,j,rows;printf("Enter the number of rows: ");scanf("%d",&rows);for(i=rows;i>=1;--i){for(j=1;j<=i;++j){printf("* ");}printf("\n");}return 0;
}

用 * 打印金字塔

** * ** * * * ** * * * * * *
* * * * * * * * *

源代码：


#include <stdio.h>
int main()
{int i,space,rows,k=0;printf("Enter the number of rows: ");scanf("%d",&rows);for(i=1;i<=rows;++i){for(space=1;space<=rows-i;++space){printf("  ");}while(k!=2*i-1){printf("* ");++k;}k=0;printf("\n");}return 0;
}

五、简单的加减乘除计算器

源代码：


/* Source code to create a simple calculator for addition, subtraction, multiplication and division using switch...case statement in C programming. */
# include <stdio.h>
int main()
{char o;float num1,num2;printf("Enter operator either + or - or * or divide : ");scanf("%c",&o);printf("Enter two operands: ");scanf("%f%f",&num1,&num2);switch(o) {case '+':printf("%.1f + %.1f = %.1f",num1, num2, num1+num2);break;case '-':printf("%.1f - %.1f = %.1f",num1, num2, num1-num2);break;case '*':printf("%.1f * %.1f = %.1f",num1, num2, num1*num2);break;case '/':printf("%.1f / %.1f = %.1f",num1, num2, num1/num2);break;default:/* If operator is other than +, -, * or /, error message is shown */printf("Error! operator is not correct");break;}return 0;
}

结果输出：


Enter operator either + or - or * or divide : -
Enter two operands: 3.4
8.4
3.4 - 8.4 = -5.0

六、检查一个数能不能表示成两个质数之和

源代码：


#include <stdio.h>
int prime(int n);
int main()
{int n, i, flag=0;printf("Enter a positive integer: ");scanf("%d",&n);for(i=2; i<=n/2; ++i){if (prime(i)!=0){if ( prime(n-i)!=0){printf("%d = %d + %d\n", n, i, n-i);flag=1;}}}if (flag==0)printf("%d can't be expressed as sum of two prime numbers.",n);return 0;
}/* Function to check prime number */
int prime(int n)
{int i, flag=1;for(i=2; i<=n/2; ++i)if(n%i==0)flag=0;return flag;
}

结果输出：


Enter a positive integer: 34
34 = 3 + 31
34 = 5 + 29
34 = 11 + 23
34 = 17 + 17

七、用递归的方式颠倒字符串

源代码：

/* Example to reverse a sentence entered by user without using strings. */
#include <stdio.h>
void Reverse();
int main()
{printf("Enter a sentence: ");Reverse();return 0;
}void Reverse()
{char c;scanf("%c",&c);if( c != '\n'){Reverse();printf("%c",c);}
}

结果输出：


Enter a sentence: margorp emosewa
awesome program

八、实现二进制与十进制之间的相互转换

源代码：


/* C programming source code to convert either binary to decimal or decimal to binary according to data entered by user. */
#include <stdio.h>
#include <math.h>
int binary_decimal(int n);
int decimal_binary(int n);
int main()
{int n;char c;printf("Instructions:\n");printf("1. Enter alphabet 'd' to convert binary to decimal.\n");printf("2. Enter alphabet 'b' to convert decimal to binary.\n");scanf("%c",&c);if (c =='d' || c == 'D'){printf("Enter a binary number: ");scanf("%d", &n);printf("%d in binary = %d in decimal", n, binary_decimal(n));}if (c =='b' || c == 'B'){printf("Enter a decimal number: ");scanf("%d", &n);printf("%d in decimal = %d in binary", n, decimal_binary(n));}return 0;
}/* Function to convert decimal to binary.*/
int decimal_binary(int n)
{int rem, i=1, binary=0;while (n!=0){rem=n%2;n/=2;binary+=rem*i;i*=10;}return binary;
}/* Function to convert binary to decimal.*/
int binary_decimal(int n)
{int decimal=0, i=0, rem;while (n!=0){rem = n%10;n/=10;decimal += rem*pow(2,i);++i;}return decimal;
}

结果输出：

九、使用多维数组实现两个矩阵的相加

源代码：


#include <stdio.h>
int main()
{int r,c,a[100][100],b[100][100],sum[100][100],i,j;printf("Enter number of rows (between 1 and 100): ");scanf("%d",&r);printf("Enter number of columns (between 1 and 100): ");scanf("%d",&c);printf("\nEnter elements of 1st matrix:\n");/* Storing elements of first matrix entered by user. */for(i=0;i<r;++i)for(j=0;j<c;++j){printf("Enter element a%d%d: ",i+1,j+1);scanf("%d",&a[i][j]);}/* Storing elements of second matrix entered by user. */printf("Enter elements of 2nd matrix:\n");for(i=0;i<r;++i)for(j=0;j<c;++j){printf("Enter element a%d%d: ",i+1,j+1);scanf("%d",&b[i][j]);}/*Adding Two matrices */for(i=0;i<r;++i)for(j=0;j<c;++j)sum[i][j]=a[i][j]+b[i][j];/* Displaying the resultant sum matrix. */printf("\nSum of two matrix is: \n\n");for(i=0;i<r;++i)for(j=0;j<c;++j){printf("%d   ",sum[i][j]);if(j==c-1)printf("\n\n");}return 0;
}

结果输出：
在这里插入图片描述

十、矩阵转置

源代码：

#include <stdio.h>
int main()
{int a[10][10], trans[10][10], r, c, i, j;printf("Enter rows and column of matrix: ");scanf("%d %d", &r, &c);/* Storing element of matrix entered by user in array a[][]. */printf("\nEnter elements of matrix:\n");for(i=0; i<r; ++i)for(j=0; j<c; ++j){printf("Enter elements a%d%d: ",i+1,j+1);scanf("%d",&a[i][j]);}/* Displaying the matrix a[][] */printf("\nEntered Matrix: \n");for(i=0; i<r; ++i)for(j=0; j<c; ++j){printf("%d  ",a[i][j]);if(j==c-1)printf("\n\n");}/* Finding transpose of matrix a[][] and storing it in array trans[][]. */for(i=0; i<r; ++i)for(j=0; j<c; ++j){trans[j][i]=a[i][j];}/* Displaying the transpose,i.e, Displaying array trans[][]. */printf("\nTranspose of Matrix:\n");for(i=0; i<c; ++i)for(j=0; j<r; ++j){printf("%d  ",trans[i][j]);if(j==r-1)printf("\n\n");}return 0;
}