10个经典的C语言面试基础算法及代码

浅浅的花香味﹌ 2022-08-02 13:57 219阅读 0赞

## 1、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+

也可以使用下面的源代码：

/* Displaying Fibonacci series up to certain number entered by user. */
     
    #include <stdio.h>
    int main()
    {
      int t1=0, t2=1, display=0, num;
      printf("Enter an integer: ");
      scanf("%d",&num);
      printf("Fibonacci Series: %d+%d+", t1, t2); /* Displaying first two terms */
      display=t1+t2;
      while(display<num)
      {
          printf("%d+",display);
          t1=t2;
          t2=display;
          display=t1+t2;
      }
      return 0;
    }

结果输出：

Enter an integer: 200
    Fibonacci Series: 0+1+1+2+3+5+8+13+21+34+55+89+144+

## 2、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);
      else
          printf("%d is not a palindrome.",n);
      return 0;
    }

结果输出：

Enter an integer: 12321
    12321 is a palindrome.

## 3、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);
      else
          printf("%d is not a prime number.",n);
      return 0;
    }

结果输出：

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

## 4、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。

1
    1 2
    1 2 3
    1 2 3 4
    1 2 3 4 5

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;
    }

用 \* 打印倒金字塔

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

源代码：

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

## 5、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

## 6、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;
    }
    int prime(int n)      /* Function to check prime number */
    {
        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

## 7、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

## 8、实现二进制与十进制之间的相互转换 ##

/* 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;
    }
     
    int decimal_binary(int n)  /* Function to convert decimal to binary.*/
    {
        int rem, i=1, binary=0;
        while (n!=0)
        {
            rem=n%2;
            n/=2;
            binary+=rem*i;
            i*=10;
        }
        return binary;
    }
     
    int binary_decimal(int n) /* Function to convert binary to decimal.*/
     
    {
        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：

![10-2][]

## 9、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：

![matrix-add][]

## 10、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;
    }

结果输出：

![reverse-matrix][]

[10-2]: http://www.codeceo.com/wp-content/uploads/2014/11/10-2.png
[matrix-add]: http://www.codeceo.com/wp-content/uploads/2014/11/matrix-add.png
[reverse-matrix]: http://www.codeceo.com/wp-content/uploads/2014/11/reverse-matrix.png