编写说明strlen、strcpy、strcat如何实现的

随便定义一个char类型字符串数组，此以char string[] = "iphone";为例。

实现strlen

char string[] = "iphone";

int i = 0;

while (string[i] != ‘\0‘) {

i ++;

}

printf("%d", i);

实现strcpy

char string1[20] = "ios";

char string2[] = "android";

//strcpy(string1,string2);

int i = 0;

while (string2[i] != ‘\0‘) {    //计算机识别到字符串后面 ‘\0’，条件成立，拷贝停止

string1[i] = string2[i];

i ++;

}

string1[i] = ‘\0‘;   //第i个字符串是‘\0’，最后给字符串加上

printf("%s", string1);

实现strcat

char string1[] = "ios";

char string2[] = "android";

long int length = strlen(string1);

int i = 0;

while (string2[i] != ‘\0‘) {      //计算机直到识别到 ‘\0’，条件成立，拼接停止

string1[i + length] = string2[i];

i ++;

}

string1[i + length] = ‘\0‘;   //加上目的字符串的长度

printf("%s", string1);