Time Conversion

Given a time in -hour AM/PM format, convert it to military (24-hour) time.

Note: - 12:00:00AM on a 12-hour clock is 00:00:00 on a 24-hour clock.
- 12:00:00PM on a 12-hour clock is 12:00:00 on a 24-hour clock.

input-> A single string  that represents a time in -hour clock format (i.e.:  or ).

Example 1:
s= 12:01:00PM

Output :
 12:01:00

Example 2:

s= 12:01:00AM

Output :
00:01:00

Example 3:

input:
s= 07:05:45PM

Output :
19:05:45

c++ implementation:

string timeConversion(string s) 
{
    int n=s.length(); string r;
    if(s[n-2]=='P')
    {
        string s1 = "";
        s1=s1+s[0];
        string s2 = "";
        s2=s2+s[1];
        
        string m=s1+s2;
        
        int v=stoi(m);
       
        if(v == 12)
        {
            for(int i=0;i<n-2;i++)
            {
                r=r+s[i];
            }
        }
        else
        {
            v=v+12;
            m=to_string(v);
            r=r+m;
            for(int i=2;i<n-2;i++)
            {
                r=r+s[i];
            }
        }
    }
    else
    {
        string s1 = "";
        s1=s1+s[0];
        string s2 = "";
        s2=s2+s[1];
        
        string m=s1+s2;
        
        int v=stoi(m);
       
        if(v == 12)
        {
            r=r+"00";
            for(int i=2;i<n-2;i++)
            {
                r=r+s[i];
            }
        }
        else
        {
            for(int i=0;i<n-2;i++)
            {
                r=r+s[i];
            }
        }
    }
    
    return r;
}

Time Complexity: O(n)

space Complexity: O(1)