day4_字符串的两头堵模型

一、求非空格的字符串长度

1、方法一 普通函数

//方法一int main01(){    //求非空格的字符串长度    char *p = "     abcdefgg    ";    int i = 0;    int j = 0;    j = strlen(p) - 1;    int count = 0;    while(isspace(p[i]) && p[i] != '\0')    {        i++;    }    while(isspace(p[j]) && p[j] != '\0')    {        j--;    }    count = j - i + 1;    printf("count:%d \n",count);    printf("Hello world!\n");    system("pause");    return 0;}

2、方法二 构造API函数

//求非空格的字符串长度//方法二 API函数void getCount(char *str,int *Pcount){    char *p = str;    int i = 0;    int j = 0;    j = strlen(p) - 1;    int count = 0;    if(str == NULL && Pcount == NULL)    {        return;    }    while(isspace(p[i]) && p[i] != '\0')    {        i++;    }    while(isspace(p[j]) && p[j] != '\0')    {        j--;    }    count = j - i + 1;    *Pcount = count;    printf("count:%d \n",*Pcount);    return 0;}

3、方法三 去除字符串前后的空格并返回新串

//去除字符串前后的空格并返回新串//方法三int trimSpace(char *str,char *newstr){    char *p = str;    int i = 0;    int j = 0;    j = strlen(p) - 1;    int count = 0;    if(str == NULL && newstr == NULL)    {        return;    }    while(isspace(p[i]) && p[i] != '\0')    {        i++;    }    while(isspace(p[j]) && p[j] != '\0')    {        j--;    }    count = j - i + 1;    strncpy(newstr,str+i,count);    newstr[count] = '\0';    return 0;}int main02(){    char *p = "     abcdefgg    ";    char buf[1024] = {0};    int getcount = 0;    getCount(p,&getcount);    printf("getcount:%d \n",getcount);    trimSpace(p,buf);    printf("buf:%s \n",buf);    printf("Hello world!\n");    system("pause");    return 0;}

4、方法四 典型错误及修改原空间

//去除字符串前后的空格并返回新串//方法四//典型错误  不能修改全局区的字符串//修改 将字符串写到字符串数组里面 修改栈区的数据int trimSpace02(char *str){    char *p = str;    int i = 0;    int j = 0;    j = strlen(p) - 1;    int count = 0;    if(str == NULL)    {        return -1;    }    while(isspace(p[i]) && p[i] != '\0')    {        i++;    }    while(isspace(p[j]) && p[j] != '\0')    {        j--;    }    count = j - i + 1;    strncpy(str,str+i,count);//error  不能向str所指向的内存空间写入数据    str[count] = '\0';    return 0;}int main(){//    char *p = "     abcdefgg    ";//数据在全局区里面 不能被修改    char buf[1024] = "     abcdefgg    ";    int getcount = 0;    trimSpace02(buf);//    printf("p:%s \n",p);     printf("buf:%s \n",buf);    printf("Hello world!\n");    system("pause");    return 0;}