JavaScript solution for week 84/part 2.

1 files changed, 45 insertions, 0 deletions

diff --git a/challenge-084/abigail/node/ch-2.js b/challenge-084/abigail/node/ch-2.js
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+++ b/challenge-084/abigail/node/ch-2.js
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+//
+// Read STDIN. Split on newlines, then on whitespace, and turn the results
+// into numbers. Since the input will be newline terminated, we have an
+// empty line to filter out.
+//
+let matrix = require      ("fs")
+           . readFileSync (0)               // Read a line.
+           . toString     ()                // Turn it into a string.
+           . split        ("\n")            // Split on newlines.
+           . filter       (_ => _)          // Remove empty (trailing) line.
+           . map (_ => _ . split (/\s+/)    // Split each line on spaces
+                         . map (_ => +_));  // Turn into numbers.
+
+let height = matrix     . length;
+let width  = matrix [0] . length;
+
+//
+// Use a cubic algorithm to count any squares will all 1s at the corners.
+// For each 0 <= x < height, 0 <= y < width, and k > 0 such that x + k < height
+// and y + k < width, we add a square if all of the following are true:
+//     matrix [x]     [y]
+//     matrix [x + k] [y]
+//     matrix [x]     [y + k]
+//     matrix [x + k] [y + k]
+//
+let count = 0;
+for (let x = 0; x < height; x ++) {
+    for (let y = 0; y < width; y ++) {
+        if (!matrix [x] [y]) {
+            continue;
+        }
+        for (let k = 1; x + k < height && y + k < width; k ++) {
+            if (matrix [x]     [y + k] &&
+                matrix [x + k] [y]     &&
+                matrix [x + k] [y + k]) {
+                count ++
+            }
+        }
+    }
+}
+
+//
+// Print the result.
+//
+console . log (count);