综合练习

1.

练习使用strlen函数

    /*
     * filename: use_strlen.c
     *
     * function: learn to use the strlen() and learn more string
     *      end of string is '\0'
     *
     * author: YourName
     *
     * version: 0.1
     *
     * date: 2011-10-27
     *
     */


    #include <stdio.h>
    #include <string.h>

    #define N 32

    int main(int argc, const char *argv[])
    {
            char str[] = "hello world";
            char arr[N] = "hello akaedu";

            printf("strlen(str) = %d\n", strlen(str));
            printf("sizeof(str) = %d\n", sizeof(str));

            printf("strlen(arr) = %d\n", strlen(arr));
            printf("sizeof(arr) = %d\n", sizeof(arr));

            return 0;
    }

2.

使用数组将一数列反向

    #include <stdio.h>

    #define N 10

    int main(int argc, const char *argv[])
    {
            int a[N], i;

            printf("enter %d number: ", N);
            for (i = 0; i < N; i++)
                    scanf("%d", &a[i]);

            printf("In reverse order: ");
            for (i = N - 1; i >= 0; i--)
                    printf(" %d", a[i]);

            printf("\n");
            
            return 0;
    }

3.

显示倒计数

    #include <stdio.h>

    void print_count(int n)
    {
            printf("T m inus %d and counting\n", n);
    }

    int main(int argc, const char *argv[])
    {
            int i;


            for (i = 10; i > 0; i--)
                    print_count(i);


            return 0;
    }

4.

计算指针变量占用的字节数

    #include <stdio.h>
    #include <string.h>


    int main(int argc, const char *argv[])
    {
            char *p = "012345";

            printf("sizeof(p) = %d, strlen(p) = %d\n", sizeof(p), strlen(p));

            printf("sizeof(char *) = %d\n", sizeof(char *));
            printf("sizeof(short *) = %d\n", sizeof(short *));
            printf("sizeof(int *) = %d\n", sizeof(int *));

            return 0;
    }

5.

使用指针将一数列反向

    #include <stdio.h>

    #define N 10

    int main(int argc, const char *argv[])
    {
            int a[N], *p;

            printf("enter %d number: ", N);
            for (p = a; p < a + N; p++)
                    scanf("%d", p);

            printf("In reverse order: ");
            for (p = a + N - 1; p >= a; p--)
                    printf(" %d", *p);

            printf("\n");
            
            return 0;
    }

6.

求以数列中的最大值

    #include <stdio.h>

    #define N 10

    int find_max(int a[], int len)
    {
            int max, i;
            max = a[0];

            for (i = 1; i < len; i++)
                    if (a[i] > max)
                            max = a[i];

            return max;
    }


    int main(int argc, const char *argv[])
    {
            
            int num[N] = {23,21,56,43,78,26,98,13,44,6};

            printf("max num is: %d\n", find_max(num, N));

            return 0;
    }

7.

练习实现strlen函数

    /*
     * filename: achieve_strlen.c
     *
     * function: achieve strlen() by yourself
     *
     * author: YourName
     *
     * version: 0.1
     *
     * date: 2011-10-27
     *
     */


    #include <stdio.h>
    #include <string.h>

    int my_strlen_fir(char s[])
    {
            int i = 0;
            int len = 0;

            //end in '\0'
            while (s[i++])
                    len++;

            return len;
    }

    int my_strlen_sec(char s[])
    {
            int len = 0;

            for ( ; (*s != '\0'); s++)
                    len++;

            return len;
    }

    int my_strlen_thi(char s[])
    {
            int len = 0;

            for ( ; *s; s++)
                    len++;

            return len;
    }

    int my_strlen_for(char s[])
    {

            int len = 0;

            for ( ; *s++; )
                    len++;

            return len;
    }

    int main(int argc, const char *argv[])
    {
            char str[] = "Hello world";

            printf("strlen(str) = %d\n", strlen(str));
            printf("my_strlen_fir(str) = %d\n", my_strlen_fir(str));
            printf("my_strlen_sec(str) = %d\n", my_strlen_sec(str));
            printf("my_strlen_thi(str) = %d\n", my_strlen_thi(str));
            printf("my_strlen_for(str) = %d\n", my_strlen_for(str));

            return 0;
    }

8.

指针的基本使用–将两个数交换

    #include <stdio.h>

    void swap_fir(int a, int b)
    {
            int tmp;

            tmp = a;
            a = b;
            b = tmp;
    }

    void swap_sec(int *a, int *b)
    {
            int tmp;

            tmp = *a;
            *a = *b;
            *b = tmp;
    }

    int main(int argc, const char *argv[])
    {
            int a = 3, b = 4;

            printf("a = %d, b = %d\n\n", a, b);

            swap_fir(a, b);
            printf("After swap_fir...\n\n");
            printf("a = %d, b = %d\n\n", a, b);
            
            a = 3, b = 4;

            printf("Again: a = %d, b = %d\n\n", a, b);
            swap_sec(&a, &b);
            printf("After swap_sec...\n\n");
            printf("a = %d, b = %d\n\n", a, b);
            
            return 0;
    }