c++从键盘上输入一个字符串求字符串长度

头文件<string.h>中有函数是计算字符串长度的
strlen()返回值为字符串的实际长度。不含'\0'

#include <iostream>
#include <string>
using namespace std;
int main()
{
cout<<"输入字符串"<<endl;
string str;
cin>>str;
cout<<"字符串的长度为"<<str.size()<<endl;
return 0;
}

#include<stdio.h>
#include <stdlib.h>
int main()
{
char* str = (char*)malloc(sizeof(char)*100);
char* temp = NULL;
int leng = 0;
scanf("%s", str);
temp = str;
while(*str)
{
str++;
leng++;
}
printf("输入字符串的长度为%d", leng);
free(temp);
return 0;
}

#include "string.h"
#include "iostream.h"

void main()
{
char* str;
cout<<"输入字符串"<<endl;
cin>>str;
cout<<"str的长度为："<<strlen(s