为什么有时候使用析构函数会让运行时间增加且系统返回值不为0?
#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
class password{
private:
int N;
char *b;
public:
password(int _n,char* _b){
N=_n;
b=_b;
}
~password(){
delete []b;
}
void cal(){
int i=0;
while(isalpha(b[i])){
b[i]=(b[i]-'a'+N)%26+'a';
i++;
}
i=0;
while(b[i])cout<<b[i++];
}
};
int main(){
int n;
char a[1000000];
cin>>n;cin>>a;
password P(n,a);
P.cal();
return 0;
}