There’s a well known way to optimise a basic search for primes, but why does it work?
There’s a well known way to optimise a basic search for primes, but why does it work?
Introduction subskybox wrote an intimidating 5-card poker hand analyzer in four lines of JavaScript. The original is somewhat tricky to understand initially:
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hands=["4 of a Kind", "Straight Flush", "Straight", "Flush", "High Card", "1 Pair", "2 Pair", "Royal Flush", "3 of a Kind", "Full House" ]; var A=14, K=13, Q=12, J=11, _ = { "♠":1, "♣":2, "♥":4, "♦":8 }; function rankPokerHand(cs,ss) { var v, i, o, s = 1<<cs[0]|1<<cs[1]|1<<cs[2]|1<<cs[3]|1<<cs[4]; for (i=-1, v=o=0; i<5; i++, o=Math.pow(2,cs[i]*4)) {v += o*((v/o&15)+1);} v = v % 15 - ((s/(s&-s) == 31) || (s == 0x403c) ? 3 : 1); v -= (ss[0] == (ss[1]|ss[2]|ss[3]|ss[4])) * ((s == 0x7c00) ? -5 : 1); document.write("Hand: " + hands[v] + (s == 0x403c?" (Ace low)":"")+"<br/>"); } |
Of course, by somewhat tricky I mean extremely tricky, and by initially I mean always. The shock and…
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