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POWhat is map[(int)x]++;What it does?
 

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  1. POWhat is map[(int)x]++;What it does?
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    <p>Hey I took part in Facebook Hacker Competition and I got a solution of this question. I solved th question in order O(K^2) but this guy solved it in O(^K). Please explain me what the code doing.</p> <pre><code> import java.io.File; import java.util.Scanner; public class FindTheMin { private long getNextMin(long[] map, long start, long k) { while (map[(int)(start)] &gt; 0) start++; return start; } public long findNth(long n, long k, long a, long b, long c, long r) { long[] cache = new long[100010]; long[] map = new long[100010]; long pre = a; for (int i = 0; i &lt; k; i++) { long num; if (i == 0) num = a; else num = (b * pre + c) % r; cache[i] = num; if (num &lt;= k + 1) map[(int) num]++; pre = num; } pre = getNextMin(map, 0, k); cache[(int)k] = pre; map[(int)pre]++; for (int i = 0; i &lt;= (int)k; i++) { long deque = cache[i]; if (deque &gt; k) { long x = getNextMin(map, pre, k); cache[i] = x; map[(int)x]++; pre = x; } else { if (deque &lt; pre) { if(map[(int)deque] == 1) { cache[i] = deque; pre = deque; continue; } } map[(int)deque]--; long x = getNextMin(map, pre, k); cache[i] = x; pre = x; map[(int)x]++; } } return cache[(int)((n - 1) % (k + 1))]; } public static void main(String[] args) { try { Scanner s = new Scanner(new File("in.txt")); int m = s.nextInt(); FindTheMin f = new FindTheMin(); for (int i = 1; i &lt;= m; i++) { int n, k, a, b, c, r; n = s.nextInt(); k = s.nextInt(); a = s.nextInt(); b = s.nextInt(); c = s.nextInt(); r = s.nextInt(); System.out.println("Case #" + i + ": " + f.findNth(n, k, a, b, c, r)); } } catch (Exception e) { e.printStackTrace(); } } } </code></pre> <p>And what are the best ways to learn things like this. the best way to learn java? This was the question <a href="https://www.facebook.com/hackercup/problems.php?pid=494433657264959&amp;round=185564241586420" rel="nofollow">https://www.facebook.com/hackercup/problems.php?pid=494433657264959&amp;round=185564241586420</a></p>
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    1. USKeith Miller
    1. USAtul
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    1. COwhat do you mean by **O(^K)** ?
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      1. POWhat is map[(int)x]++;What it does?
      1. USMrSmith42
    2. COWhy is it tagged [c]?
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      1. USAnT
    3. COCould you please post the question for these of us who prefer to not have facebook accounts?
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      1. USdasblinkenlight
 

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