Merge pull request cp-algorithms#688 from rajatdiptabiswas/patch-3

jakobkogler · web-flow · commit 72c81dbbe05e · 2021-03-24T20:42:15.000+01:00
Fix typo
diff --git a/src/combinatorics/inclusion-exclusion.md b/src/combinatorics/inclusion-exclusion.md
@@ -229,7 +229,7 @@ Notice first that we can easily count the number of strings that satisfy at once
 
 Learn now to solve the first version of the problem: when the string must satisfy exactly $k$ of the patterns.
 
-To solve it, iterate and fix a specific subset $X$ from the set of patterns consisting of $k$ patterns. Then we have to count the number of strings that satisfy this set of patterns, and only matches it, that is, they don't match any other pattern. We will use the inclusion-exclusion principle in a slightly different manner: we sum on all supersets $Y$ (subsets from the original set of strings that contain $X$), and either add to the current answer of subtract it from the number of strings:
+To solve it, iterate and fix a specific subset $X$ from the set of patterns consisting of $k$ patterns. Then we have to count the number of strings that satisfy this set of patterns, and only matches it, that is, they don't match any other pattern. We will use the inclusion-exclusion principle in a slightly different manner: we sum on all supersets $Y$ (subsets from the original set of strings that contain $X$), and either add to the current answer or subtract it from the number of strings:
 
 $$ ans(X) = \sum_{Y \supseteq X} (-1)^{|Y|-k} \cdot f(Y) $$
 
