Lua solution for week 128, part 2

1 files changed, 67 insertions, 0 deletions

diff --git a/challenge-128/abigail/lua/ch-2.lua b/challenge-128/abigail/lua/ch-2.lua
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+++ b/challenge-128/abigail/lua/ch-2.lua
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+#!/opt/local/bin/lua
+
+--
+-- See ../README.md
+--
+
+--
+-- Run as: lua ch-1.lua < input-file
+--
+
+
+--
+-- Read the input, and convert it to minutes (from midnight)
+--
+
+local arrivals   = {}
+local departures = {}
+
+for hour, minute in io . read ("*l") : gmatch ("([0-9][0-9]):([0-9][0-9])") do
+    arrivals   [#arrivals   + 1] = 60 * tonumber (hour) + tonumber (minute)
+end
+for hour, minute in io . read ("*l") : gmatch ("([0-9][0-9]):([0-9][0-9])") do
+    departures [#departures + 1] = 60 * tonumber (hour) + tonumber (minute)
+end
+
+--
+-- Initialize the trains array, which counts the number of trains
+-- in the station on each minute of the day.
+--
+local trains = {}
+for i = 0, 24 * 60 - 1 do
+    trains [i] = 0
+end
+
+--
+-- Process each train
+--
+for i, arrival in ipairs (arrivals) do
+    local departure = departures [i]
+    if arrival < departure then
+        for i = arrival, departure do
+            trains [i] = trains [i] + 1
+        end
+    else
+        for i = 0, arrival do
+            trains [i] = trains [i] + 1
+        end
+        for i = departures, 24 * 60 - 1 do
+            trains [i] = trains [i] + 1
+        end
+    end
+end
+
+--
+-- Find the maximum
+--
+local max = 0
+for i, count in ipairs (trains) do
+    if max < count then
+       max = count
+    end
+end
+
+--
+-- And print it
+--
+print (max)