C语言字符串及其函数

#include<stdio.h>
int main(){
    printf("输入一个整数");
    int n;
    scanf("%d",&n); 
    char a[n];
    getchar();
    for(int i=0;i<n;i++){
        scanf("%c",&a[i]);
    }
    a[n]='\0';
    printf("%s",a);
    
} 

strlen函数

#include<stdio.h>
#include<string.h>
//最后一位还要存储一个'/0' 
int main(){
    char str[]="大家好才是正的哈";
    printf("%s\n",str);
    printf("sizeiof的输出：%d",sizeof(str));
printf("strlen的输出%u",strlen(str));
}

strcpy

#include<stdio.h>
#include<string.h>
int main()
{
    char str1[]="I love China";
    char str2[]="I love girl";
    char str3[50];
    strcpy(str1,str2);//打印到出现'/0'的时候读取停止 
    strcpy(str3,"copy successful");
    printf("str1=%s\n",str1);
    printf("str2=%s\n",str2);
        printf("str3=%s\n",str3);    
} 

strncpy

#include<stdio.h>
#include<string.h>
int main()
{
    char str1[]="IloveChina";
    char str2[]="qweedadafc";
    char str3[50];
    strncpy(str1,str2,7);//控制到拷贝的 
    str1[7]='\0';
    strcpy(str3,"copy successful");
    printf("str1=%s\n",str1);
    printf("str2=%s\n",str2);
        printf("str3=%s\n",str3);    
} 

strcat

#include<stdio.h>
#include<string.h>
//字符串的拼接 
//strncat会自动添加结束符 
int main()
{
    char str1[]="I love China";
    char str2[]="I love girl";
    strcat(str1," ");
    strcat(str1,str2);//拷贝到出现'/0'的时候读取停止 
    printf("str1=%s\n",str1);
    printf("str2=%s\n",str2);
} 

strcmp

#include<stdio.h>
#include<string.h>
int main()
//比较字符串 
{
    char str1[]="dalao";
    char str2[]="dalao";
    if(!strcmp(str1,str2)){
        printf("它们相等");
    }else{
        printf("它们不等");
    }
} 

 对于函数的实现;

拷贝字符串 —— strcpy 和 strncpy 函数,

 

#include<iostream>
using namespace std;
#define MAX 1024
int main(){
	char str1[MAX];
	char str2[MAX];
	char *target1=str1;
	char *target2=str2;
	printf("输入一个字符串到str1中");
	fgets(str1,MAX,stdin);
	printf("开始拷贝str1内容到str2\n");
	while((*target2++=*target1++)!='\0'){
	}
	printf("拷贝完毕");
	printf("%s",str2);
}

 

#include <stdio.h>

#define MAX 1024

int main()
{
        char str1[MAX];
        char str2[MAX];

        char *target1 = str1;
        char *target2 = str2;

        char ch;
        int n;

        printf("请输入一个字符串到 str1 中：");
        fgets(str1, MAX, stdin);

        printf("请输入需要拷贝的字符个数：");
        scanf("%d", &n);

        printf("开始拷贝 str1 的内容到 str2 中...\n");
        while (n--)
        {
               ch = *target2++ = *target1++;
               if (ch == '\0')
               {
                       break;
               }
               if ((int)ch < 0)
               {
                       *target2++ = *target1++;
                       *target2++ = *target1++;
               }
        }

        *target2 = '\0';

        printf("拷贝完毕！\n");
        printf("现在，str2 中的内容是：%s\n", str2);

        return 0;
}

连接字符串 —— strcat 和 strncat 函数

#include<iostream>
using namespace std;
#define MAX 1024
int main(){
	char str1[2*MAX];//确保连接后不越界
	char str2[MAX];
	char *target1=str1;
	char *target2=str2;
	printf("输入第一个字符串") ;
	fgets(str1,MAX,stdin);
	printf("请输入第二个字符");
	fgets(str2,MAX,stdin);
	//将指针指向第一个字符的末尾处
	while(*target1++!='\0');
	target1-=2;//去掉/0 与/n
	//连接字符串
	while((*target1++=*target2++)!='\0');
	printf("%s",str1);
	 
}

 比较字符串 —— strcmp 和 strncmp 函数R+o

 

#include <stdio.h>

#define MAX 1024

int main()
{
        char str1[MAX];
        char str2[MAX];

        char *target1 = str1;
        char *target2 = str2;

        int index = 1;

        printf("请输入第一个字符串：");
        fgets(str1, MAX, stdin);

        printf("请输入第二个字符串：");
        fgets(str2, MAX, stdin);

        while (*target1 != '\0' && *target2 != '\0')
        {
                if (*target1++ != *target2++)
                {
                       break;
                }
                index++;
        }

        if (*target1 == '\0' && *target2 == '\0')
        {
                printf("两个字符串完全一致！\n");
        }
        else
        {
                printf("两个字符串不完全相同，第 %d 个字符出现不同！\n", index);
        }

        return 0;
}

#include <stdio.h>

#define MAX 1024

int main()
{
        char str1[MAX];
        char str2[MAX];

        char *target1 = str1;
        char *target2 = str2;

        char ch;
        int index = 1, n;

        printf("请输入第一个字符串：");
        fgets(str1, MAX, stdin);

        printf("请输入第二个字符串：");
        fgets(str2, MAX, stdin);

        printf("请输入需要对比的字符个数：");
        scanf("%d", &n);

        while (n && *target1 != '\0' && *target2 != '\0')
        {
                ch = *target1;
                if (ch < 0)
                {
                        if (*target1++ != *target2++ || *target1++ != *target2++)
                        {
                                break;
                        }
                }
                if (*target1++ != *target2++)
                {
                       break;
                }
                index++;
                n--;
        }

        if ((n == 0) || (*target1 == '\0' && *target2 == '\0'))
        {
                printf("两个字符串的前 %d 个字符完全相同！\n", index);
        }
        else
        {
                printf("两个字符串不完全相同，第 %d 个字符出现不同！\n", index);
        }

        return 0;
}