2021-01: Add Nim solution

Signed-off-by: AKU <tom@tdpain.net>

challenges/2021/01-sonarSweep/nim/challenge.nim

@@ -0,0 +1,33 @@
+import std/strutils
+import std/sequtils
+
+proc loadInput(): string =
+    return readFile("input.txt")
+
+proc parseInput(instr: string): seq[int] =
+    for item in split(instr, "\n"):
+        if item == "":
+            continue
+        let n = parseInt(item)
+        result.add(n)
+
+let input = parseInput(loadInput())
+
+proc countIncreases(data: seq[int]): int = 
+    for i in countup(1, data.len()-1):
+        if data[i] > data[i-1]:
+            result = result + 1
+
+proc partOne(): int =
+    return countIncreases(input)
+
+proc partTwo(): int =
+    var sums: seq[int]
+    for i in countup(0, len(input)-3):
+        sums.add(
+            (@input[i..i+2]).foldl(a+b),
+        )
+    return countIncreases(sums)
+
+echo "Part one: " & $partOne()
+echo "Part two: " & $partTwo()