[UVa] 12444 - Bits & Pieces

Method: Bitmasking, Bit manipulation
Trick: Analyze the problem a bit with the given Samples.
When for a particular bit
C = 1 & D = 1, obviously both the numbers have to have 1 in that position
C = 0 & D = 1, if this case occurs for the first time make the bit in B = 1 & A = 0, otherwise B = 0 & A = 1. This ensures |B-A] Minimality & A<=B.
No other combination is possible.

/* Faith-M */

//Headers
#include <set>
#include <map>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <cctype>
#include <cstdio>
#include <string>
#include <vector>
#include <cassert>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <climits>
#include <clocale>
//Defines
#define pow2(i) (1<<i)
#define bit(i) (1<<i)
#define isOdd(i) (i&1)
#define isEven(i) (!(i&1))
#define isPrime(i) ((i==2) || ((i&1) && !pTest[i])) //pTest has to be the bool array's name
#define sz(i) i.size()
#define vec(type,name) vector< type > name
#define rep(i,a,b) for(int i=a ; i<=b ; i++)
#define swap(type,a,b) {type t=a; a=b; b=t;}
#define sum(a,n) ( (n*(n+1)/2) - (a-1)*a/2 )
#define iscap(i) (i>='A'&&i<='Z')
#define issmall(i) (i>='a'&&i<='z')
#define isnum(i) (i>='0'&&i<='9')
#define issymbol(i) (!(i>='a'&&i<='z') && !(i>='A'&&i<='Z') && !(i>='0'&&i<='9'))
#define mk(i,j) make_pair(i,j)
#define ERROR 1e-11
//Type Defs
typedef long long lint;
typedef unsigned long long ulint;
typedef long double ldouble;

using namespace std;

pair <lint, lint> find( lint c, lint d )
{
    lint a=0, b=0, bit_c, bit_d;
    bool fbit=true;
    int i;

    for (i=31 ; i>=0 ; i--)
    {
        if ((1<<i)&c) bit_c = 1;
        else bit_c = 0;

        if ((1<<i)&d) bit_d = 1;
        else bit_d = 0;

        if (bit_c == 1 && bit_d == 1)
        {
            a = a | (1<<i);
            b = b | (1<<i);
        } else if (bit_c == 0 && bit_d == 1)
        {
            if (fbit == true)
            {
                b = b | (1<<i);
            } else
            {
                a = a | (1<<i);
            }
            fbit = false;
        }
    }

    if ( (a&b) == c && (a|b) == d ) return make_pair(a,b);
    else return make_pair(-1,-1);

}

int main()
{
 //freopen("input.txt","r+",stdin);
 //freopen("output.txt","w+",stdout);/**/

 //    TEST CASE     //
 int kase=1, kounter=1;/**/

 lint c, d;

    scanf("%d",&kase);
    while (kase--)
    {
        cin >> c >> d;

        pair <lint, lint> res = find(c,d);

        if (res.first == -1) printf("-1\n");
        else cout << res.first << " " << res.second << endl;
    }


 return 0;
}

Some tricks for C/C++

Over the years I've been into coding, I've found many techniques coders use to squeeze out more time out of a program or decrease their coding time. Some of them have been given here, for reference.

Use #define as function:

#define isCaps(i) (i>='A" && i<='Z')
int main()
{
    if (isCaps('S')) printf("S is in Caps\n");
    return 0;
}

Shorten your simple for loops:

#define FOR(i, a, b) for(i=a ; i<b ; i++)
int main()
{
    int i;
    FOR(i, 1, 985)
    {
        printf("%d\n",i);
    }
    return 0;
}

Test whether a number is even or odd:

#define isEven(j) (!(j & 0x01))

Divide a number by 2:

n = n >> 1;

You can find some nice bit tricks in this link. [ Bit twiddling hacks ]
I'll add more when I get these more organized :p.