1. 实现  mystrcpy(), mystrcmp(), mystrcat(), mystrlen() ;
   #include
          
           #include
           
            int mystrlen(char *c){    int i=0;    while (c[i]!='\0')i++;    return i;}int mystrcmp(char *c1,char *c2){    int i = 0, j = 0;    for (; c1[i] != '\0'&&c2[i] != '\0'; i++)    {        if (c1[i] < c2[i])return -1;        else if (c1[i] == c2[i])continue;        else return 1;    }    return 0;}char* mystrcopy(char *c1, char *c2){    int i = 0, j = 0;    while (c2[j] != '\0')c1[i++] = c2[j++];    c1[i] = '\0';    return c1;}char* mystrcat(char *c1, char *c2){    int i = 0, j = 0;    while (c1[i] != '\0')i++;    while(c2[j] != '\0')c1[i++] = c2[j++];    c1[i] = '\0';    return c1;}int main(){    char c1[100] = "hello ", c2[100] = "woel";    printf("%d\n",mystrlen(c1));    printf("%d\n", mystrcmp(c1, c2));    mystrcat(c1, c2);    printf("%s\n", c1);    mystrcopy(c1, c2);    printf("%s\n", c1);    system("pause");    return 0;}
           
          

   2.输入一行字符串（单词和若干空格）， 输出该行单词个数。

   Input：____hello_________world_ how___are___you___\n

   　　Output:   5

#include
     
      #include
      
       int fun(char *c) {    int i = 0,cnt=0;    while (c[i] != '\0')    {        if (c[i] == ' ')        {            i++;            if (c[i] != ' ')cnt++;        }        else i++;            }    return cnt;}int main(){    char c1[100] = "hello world how are you ";    puts(c1);    printf("%d",fun(c1));    system("pause");    return 0;}
      
     

3.输入一行字符串（单词和若干空格），输出该行单词（每个单词一行）

Input：____hello_________world_ how___are___you___\n

Output:   hello

                world

                how

                are

                       You

#include
     
      #include
      
       void fun(char *c) {    int i = 0,cnt=0;    while (c[i] != '\0')    {        if (c[i] == ' ')        {            i++;            continue;        }        if (c[i] != ' ')        {            printf("%c", c[i]);            i++;            if (c[i] == ' ')printf("\n");        }            }}int main(){    char c1[100] = "hello world how are you ";    puts(c1);    fun(c1);    system("pause");    return 0;}
      
     

4.输入一行字符串，把字符串翻转 。

Input: I____am__a__student

Output: student__a__am____I

 

1、直接翻转一下

2、把每个单词找出来，原地自身翻转

#include<stdio.h>

#include<stdlib.h>

#include<string.h>

void fun1(char *c)

{

int i = strlen(c) - 1;

while (i >= 0)

{

printf("%c", c[i]);

i--;

}

//printf("\n");

}

void strcut(char *s, char *sub) //用参数sub来保存结果，所以函数不用返回值了

{

int i=0, j = 0, k = 0;

for (i = strlen(s)-1; i >=0 ; i--)

{

//printf("%c", s[i]);

if (s[i] != ' ')

{

sub[j++] = s[i];

if (s[i-1] == ' '||i==0)

{

sub[j] = '\0';

fun1(sub); printf(" ");

j = 0;

}

}

}

}

int main()

{

char c1[] = "hello world how are you ";

puts(c1);

fun1(c1);

printf("\n");

char ps[100]; //用来保存截取子串的必须是数组，不能是指针

static char s[] = "hello world how are you ";

strcut(s, ps);

//printf("%s\n", ps);

system("pause");

return 0;

}