Openjudge noi 1.13 46: octal to decimal

【 Topic link 】

OpenJudge NOI 1.13 46: Octal to decimal

【 Topic test site 】

1. Number system

2. Input and output x Base string

• Use scanf or printf

Base number	Format control specifier
Decimal system	%d
octal	%o
Hexadecimal	%x

example ： Enter octal digits to a
scanf("%o", &a);

• Use cin or cout

Base number	specifier
Decimal system	dec
octal	oct
Hexadecimal	hex

example ： Enter octal digits to a
cin >> oct >> a

【 Their thinking 】

solution 1： Number conversion

Basic number system conversion , To convert an original number into a value through a combination of numbers , Then the value is divided into digits under the target base , Get the digit string of the target base .

solution 2：（ Clever ） Input and output x Base string

To borrow scanf/printf or cin/cout Specific methods in , Can handle decimal 、 octal 、 Conversion of hexadecimal digits .
This is an ingenious method , Not a general method . Just to understand .

【 Solution code 】

solution 1：

• C++ style

#include <bits/stdc++.h>
using namespace std;
int main()
{
    
    int val = 0;
    string s;
    cin >> s;
    for(int i = 0; i < s.length(); ++i)
        val = val * 8 + s[i] - '0';
    cout << val;    
    return 0;
}

• C style

#include <bits/stdc++.h>
using namespace std;
int toVal(char s[], int k)//k Base string s Convert to value  
{
    
    int len = strlen(s), val = 0;
    for(int i = 0; i < len; ++i)
        val = val * k + s[i] - '0';
    return val;
}
int main()
{
    
    char s[20];
    scanf("%s", s);
    printf("%d", toVal(s, 8));// Direct output value , It's the decimal system  
    return 0;
}

solution 2： Input and output x Base string

• Use scanf/printf

#include <bits/stdc++.h>
using namespace std;
int main()
{
    
    int a;
    scanf("%o", &a);
    printf("%d", a); 
    return 0;
}

• Use cin/cout

#include <bits/stdc++.h>
using namespace std;
int main()
{
    
    int a;
    cin >> oct >> a;
    cout << a;
    return 0;
}