Wikipedia link.

ShaneMcC · Dec 11, 2018 · 82a4e98 · 82a4e98
1 parent 6344589
commit 82a4e98
Showing 1 changed file with 1 addition and 0 deletions.
diff --git a/11/run.php b/11/run.php
@@ -15,6 +15,7 @@ function getPowerLevel($x, $y, $gridSerial) {
 	}
 
 	// Generate prefix-sum grid.
+	// https://en.wikipedia.org/wiki/Summed-area_table
 	foreach (yieldXY(0, 0, 300, 300) as $x => $y) {
 		// Prefix Sum is the power value of the whole square from 0,0 to x,y.