#字符串倒序输出

实现逻辑，通过strlen获取字符串长度，然后通过 len/2 进行交叉赋值，这里需要注意，不需要考虑len是奇数还是偶数的问题。

如果len是奇数，最后一个字符就不需要倒序，如果是偶数，最后两个字符就倒序。

#include "stdio.h"void rechange_str(char *str)
{int i, len;char tmp;if (NULL == str) {return ;}len = strlen(str);for (i = 0; i < len/2; i   ) {tmp = str[i];str[i] = str[len-i-1];str[len-i-1] = tmp;}
}int main(void)
{char str[20] = "hello,world";printf("%s\n",str);rechange_str(str);printf("%s\n",str);return (0);
} 

程序输出

hello,world
dlrow,olleh--------------------------------
Process exited after 0.02841 seconds with return value 0
请按任意键继续. . .

#整型转字符串

实现逻辑，每个整数看其转换进制，从个位到十位百位都可以通过%操作加上/操作获得，再用一个字符数组保存0-F。

用个位数对应值转为字符，注意转换出的字符串是反向的,还要考虑传入的若是负数如何处理，再用翻转字符串完成最后整个操作

下面这段代码需要好好研究一下，最好自己运行试试。

#include "stdio.h"char *sky_itoa(int value, char *str, unsigned int radix)
{char list[] = "0123456789ABCDEF";unsigned int tmp_value;int i, j, k;if (NULL == str) {return NULL;}if (2 != radix && 8 != radix && 10 != radix && 16 != radix) {return NULL;}i = 0;k = 0;if (radix == 10 && value < 0) {tmp_value = (unsigned int)(0 - value);str[i  ] = '-';k = 1;} else {tmp_value = (unsigned int)value;}do {str[i  ] = list[tmp_value%radix];tmp_value /= radix;} while(tmp_value);str[i] = '\0';//翻转char tmp;for (j = k; j < (i k)/2; j  ) {tmp = str[j];str[j] = str[i k-j-1];str[i k-j-1] = tmp;}return str;
}int main(void)
{int a = 1254545;char str[100] ={0};printf("%s\n",sky_itoa(a,str,2));printf("%s\n",sky_itoa(a,str,8));printf("%s\n",sky_itoa(a,str,10));printf("%s\n",sky_itoa(a,str,16));return (0);
} 

程序输出

100110010010010010001
4622221
1254545
132491--------------------------------
Process exited after 0.02963 seconds with return value 0
请按任意键继续. . .

#字符串复制

实现逻辑，逐个赋值直到遇到'\0'停止即可

#include "stdio.h"char *sky_strcpy(char *dst, const char *str)
{if (NULL == dst ||  NULL == str) {return NULL;}char *ret = dst;while (*str != '\0') {*dst    = *str   ;}return ret;
} int main(void)
{char str_1[100] = "hello,world";char str[100] ={0};sky_strcpy(str,str_1);printf("str_1:%s\n",str_1);printf("str:%s\n",str);return (0);
} 

程序输出

str_1:hello,world
str:hello,world--------------------------------
Process exited after 0.03334 seconds with return value 0
请按任意键继续. . .

#字符串比较

1、正常比较是否相同 实现逻辑，判断字符串长度是否相同，若相同逐个比较字符是否相同

#include "stdio.h"int sky_strcmp(char *dst, char *str)
{int i, len;if (NULL == dst || NULL == str) {return 0;}if (strlen(dst) != strlen(str)) {return 0;}len = strlen(dst);for (i = 0; i < len; i  ) {if (*dst   != *str  ) {return 0;}}return 1;
} int main(void)
{char str_1[100] = "hello,world";char str_2[100] = "hello,world";char str[100] = "adfs";printf("%d\n",sky_strcmp(str_1,str));printf("%d\n",sky_strcmp(str_1,str_2));return (0);
} 

程序输出

0
1--------------------------------
Process exited after 0.02802 seconds with return value 0
请按任意键继续. . .

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