深入攻克c语言--day03

实现 mystrcpy(), mystrcmp(), mystrcat(), mystrlen() ;

#include<stdio.h>
#include<stdlib.h>

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<stdio.h>
#include<stdlib.h>

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<stdio.h>
#include<stdlib.h>

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;
}

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深入攻克c语言--day03

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