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  1. Practice
  2. Algorithms
  3. Warmup
  4. Birthday Cake Candles
  5. Discussions

Birthday Cake Candles

  • apghr + 15 comments
    while(std::cin >> n)
        max < n ? c = !!(max = n) : c += max == n;

    can be translated as:

    while(std::cin >> n){ // for each candle n check:
    if(max < n) { // does n set a new record in height?
        max = n; // if that's so, then n is the new max height
        c = 1; // and the counter c must be set to 1 again. "!!" is a cheap trick to convert any value different from 0 into 1
    }
    else { // otherwise check if the new candle is as tall as max
        if (max == n)
            c++; // in that case, add 1 to counter (otherwise add 0)
    }
}
    • arpita414 + 0 comments

      Too good

    • oswald200801 + 0 comments

      Nice one !!

    • ScienceD + 1 comment

      How the hell "!!" trick work? I have no idea...

      • Gerard0 + 0 comments

        When you negate '!' a value diferent than 0 you will get 0, then if you negate 0 you will get 1 so..

        !anyNonZeroVal == 0 !0 == 1

        !!anyNonZeroVal == 1;

    • aishwarya217 + 0 comments

      Good!

    • adityabcs93 + 0 comments

      nice one

    • lehieuminh231 + 0 comments

      nice. thank you

    • tarsum + 0 comments

      Well I came up with similar algorithm, so thumbs up. Also seems like solution in editorial goes though array twice, and this goes only once.

    • Vishwas92 + 0 comments

      hats off..

    • ichidan + 2 comments

      Nice one. I arrived at same algo in C, minus the one liner ternary. Looks neat, I like it. Although I'd be curious if there is not a small performance loss of doing:

      c = !!(expr);

      vs

      (expr);
c = 1;

      the former may require additional conditional logic depending on architecture (for instance x86 - http://riffwiki.com/MOV_(x86_instruction) - the MOV instruction doesn't affect ZeroFlag, so I'd guess CPU would have to evaluate whether your expr results in a non-zero value. It's obvious to us as we can see the wider context of the algorithm, but not the CPU)

      • kurian_benoy + 0 comments

        thanks

      • viigihabe + 0 comments

        It is not CPU that analyses your c++, the compiler does. CPU doesn't "thin" but compiler does. It is really pointless to "optimize" your code this way because compiler is required to emit assembly that does what is ment but in which order and through which instructions, it is not specified. You better belive it does good job. You express c++ although it is slower than ++c: there is no way the compiler would use slower version if it doesn't afect the program flow. With no optimization flags may be.

    • lakshay91dutt + 0 comments
      [deleted]
    • rahulsahu_blog + 0 comments

      This is brilliant!

    • gharibakhamis + 0 comments

      nice why didn't i think of this sooner

    • parvpareek + 0 comments

      TYSM!! Helped me a lot..

    • sabahat_usman_su + 0 comments

      I did the same thing but my code fails for some tests :O

    • jagmeetsingh + 0 comments

      I tried same in java. It worked! Thanks (:

      int temp, max = 0, result = 0, n;
for (int i = 0; i < arCount; i++) {
    n = scanner.nextInt();
    temp = (max < n) ? (result = ((max = n) >= 0) ? 1 : 1) : (result += (n == max) ? 1 : 0);
    }