Add 2017 solutions

2017/Advent1.playground/Pages/Day 2 - 2.xcplaygroundpage/Contents.swift

@@ -0,0 +1,61 @@
+//: [Previous](@previous)
+
+//: [Previous](@previous)
+
+let data = """
+104    240    147    246    123    175    372    71    116    230    260    118    202    270    277    292
+740    755    135    205    429    822    844    90    828    115    440    805    526    91    519    373
+1630    991    1471    1294    52    1566    50    1508    1367    1489    55    547    342    512    323    51
+1356    178    1705    119    1609    1409    245    292    1434    694    405    1692    247    193    1482    1407
+2235    3321    3647    212    1402    3711    3641    1287    2725    692    1235    3100    123    144    104    101
+1306    1224    1238    186    751    734    1204    1275    366    149    1114    166    1118    239    153    943
+132    1547    1564    512    2643    2376    2324    2159    1658    107    1604    145    2407    131    2073    1878
+1845    91    1662    108    92    1706    1815    1797    1728    1150    1576    83    97    547    1267    261
+78    558    419    435    565    107    638    173    93    580    338    52    633    256    377    73
+1143    3516    4205    3523    148    401    3996    3588    300    1117    2915    1649    135    134    182    267
+156    2760    1816    2442    2985    990    2598    1273    167    821    138    141    2761    2399    1330    1276
+3746    3979    2989    161    4554    156    3359    173    3319    192    3707    264    762    2672    4423    2924
+3098    4309    4971    5439    131    171    5544    595    154    571    4399    4294    160    6201    4329    5244
+728    249    1728    305    2407    239    691    2241    2545    1543    55    2303    1020    753    193    1638
+260    352    190    877    118    77    1065    1105    1085    1032    71    87    851    56    1161    667
+1763    464    182    1932    1209    640    545    931    1979    197    1774    174    2074    1800    939    161
+"""
+    .split(separator: "\n")
+    .map {
+        $0.split(whereSeparator: \.isWhitespace)
+            .map { Int($0)! }
+    }
+
+extension Collection  {
+    func pairs() -> [(Element, Element)] {
+        var result: [(Element, Element)] = []
+        for index in indices {
+            let first = self[index]
+            for second in self[..<index] {
+                result.append((first, second))
+            }
+        }
+        return result
+    }
+    
+}
+
+["a", "b", "c"].pairs()
+
+let checksum = data.reduce(into: 0) { result, row in
+    for (a, b) in row.pairs() {
+        let smaller = min(a, b)
+        let larger = max(a, b)
+        
+        if larger % smaller == 0 {
+            result += larger / smaller
+            break
+        }
+    }
+}
+
+checksum
+
+//: [Next](@next)
+
+//: [Next](@next)