C语言数组与指针(四)

//不能对未初始化的指针取值 *p,会导致内存错误,因为p指针只是分配了指针内存，没有分配数据内存，4不知道会被存到哪里；应该分配一个已存在指针地址

    int *p;

    int f = 4;

    *p = 4;    //错误:

    p = &f;    //正确: 将一个已经分配的指针地址赋值给 p

数组初始化

int array(){        //1、整型数组    int i_ary[] = {1,3,5}; //i_ary 就是指针,是数组首元素的地址，    printf("i_ary数组通过地址获取每元素值:\n默认首元素--%d\n [0]--%d\n [1]--%d\n [2]--%d\n",*i_ary,*(i_ary+0),*(i_ary+1),*(i_ary+2));    /*     默认首元素--1     [0]--1     [1]--3     [2]--5     */        int ii_ary[2] = {1,2};            //2、浮点数组    float f_ary[] = {1.1,2.2,3.3};    float ff_ary[(int) 2.5];    ff_ary[1] = 1.2;    ff_ary[0] = 2.343;                //3、字符数组    char c_ary[] = {'a','b','d'};    char c2_ary[] = "ABD"; //字符串会自动添加 '\0'结束符，数组元素个数 = 实参+结束符                //TODO:先声明后赋值    //如果只初始化一部分，未必初始化部分会被设置为0    int l_ary[4];    l_ary[0] = 1;    l_ary[1] = 2;    l_ary[2] = 3;    l_ary[3] = 4;    printf("下标1的元素:%d\r\n",l_ary[1]);    scanf("%d",&l_ary[1]);    printf("输出:%d\n",l_ary[1]);            //C99新特性:指定下标初始化    int c99_ary[10] = {[1]=3,[3]=10,[8]=44};    /**     * 输出结果:       (int [10]) c99_ary = ([0] = 0, [1] = 3, [2] = 0, [3] = 10, [4] = 0, [5] = 0, [6] = 0, [7] = 0, [8] = 44, [9] = 0)     */    }

多维数组

int arrays(){    //5个由12个整数组成的数组的数组,每个元素包含12个整型数组    int i_ary[5][12];    //每个元素的类型是 int[12]        //多维数组赋值    int ii_ary[5][12] = {{1,2},{2,3,3,5,7,8},{35,333,1},{32,3,111},{456,66,999}};    int m[3][5] = {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};    int aba = 10;    int *m2[] = {&aba,&aba};    int *m3[2][2] = {{&aba,&aba},{&aba,&aba}};        char sdf[2][3] = {{"sf"},{"df"}};    char sdf2[2][3] = {"sf","df"};        //指针数组    char *cc_ary[] = {"adfdf","dfffd","sdfdf"};    char *wer[] = {"dsf","dfdf","dfdf"};    char *wer2[] = {"dsfdf"};    char *wer3[2][2] = {"dsf","dfdf"};        //字符数组    char aa[] = {"dfdfdf"};    char aa2[2][3] = {{"df"},{"aa"}};        return 0;}

数组与指针(参考网络)

int arrayAndPointer(){    static int m[3][4]={0,1,2,3,4,5,6,7,8,9,10,11};/* 定义二维数组m并初始化*/    int (*p)[4];//数组指针  p是指针，指向一维数组,每个一维数组有4个int元素    int i,j;    int *b;    int *q[3] = {b,b,b};//指针数组 q是数组，数组元素是指针，3个int指针    p=m;    //p是指针，可以直接指向二维数组    printf("--数组指针输出元素--\n");        for(i=0;i<3;i++)/*输出二维数组中各个元素的数值*/    {        for(j=0;j<4;j++)        {            printf("%3d ",*(*(p+i)+j));                    }        printf("\n");    }    printf("\n");    for(i=0;i<3;i++,p++)//p可看成是行指针    {        printf("%3d ",**p);//每一行的第一个元素        printf("%3d ",*(*p+1));//每一行的第二个元素        printf("%3d ",*(*p+2));//每一行的第三个元素        printf("%3d ",*(*p+3));//每一行的第四个元素        printf("\n");    }    printf("\n");    printf("--指针数组输出元素--\n");    for(i=0;i<3;i++)        q[i]=m[i];//q是数组，元素q[i]是指针    for(i=0;i<3;i++)    {        for(j=0;j<4;j++)        {            printf("%3d ",q[i][j]);//q[i][j]可换成*(q[i]+j)        }        printf("\n");    }    printf("\n");    q[0]=m[0];    for(i=0;i<3;i++)    {        for(j=0;j<4;j++)        {            printf("%3d ",*(q[0]+j+4*i));        }        printf("\n");    }    printf("\n");        return 0;        //_____________    printf("4的十六%#x",4);        for (int i=0; i<3; i++) {                for (int y=0; y<4; y++) {                        printf("每个元素值是:%p\n",&(m[i][y]));        }    }}

int pointer(){    //1、整形指针    int i_ary[] = {1,3,5};    int ii_ary[] = {1,2};    int *iii_ary[11];    printf("%p",i_ary);        int tt = 5;    int *b = &tt; //地址赋值给左边指针        //数组首地址赋值给指针，指针通过内存地址取值    int iiii[11] = {1,2,3}; //指针数组，元素类型为整型    printf("0=%p 1=%p",&iiii[0],&iiii[1]);    int *asdf = iiii;    int ss = *(asdf+1); //asdf[1] 等同于 *(asdf+1) ;                        //2、浮点指针                //3、char指针    char *cc_ary[] = {"adfdf","dfffd","sdfdf"};    return 0;}