From 890f953c6cf7e27b3f34b9571107ac71e3734382 Mon Sep 17 00:00:00 2001
From: Bruno Freitas Tissei <bft15@inf.ufpr.br>
Date: Thu, 1 Feb 2018 15:14:14 -0200
Subject: [PATCH] Add KMP
Signed-off-by: Bruno Freitas Tissei <bft15@inf.ufpr.br>
---
string/kmp.cpp | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)
create mode 100644 string/kmp.cpp
diff --git a/string/kmp.cpp b/string/kmp.cpp
new file mode 100644
index 0000000..f542fd4
--- /dev/null
+++ b/string/kmp.cpp
@@ -0,0 +1,44 @@
+/**
+ * Knuth-Morris-Pratt - KMP
+ *
+ * Complexity (Time):
+ * preprocess -> O(m)
+ * search -> O(n)
+ * Complexity (Space): O(n + m)
+ */
+
+int table[MAX];
+vector<int> occurs;
+
+// Build the table where table[i] is the longest prefix of patt[0..i] which is
+// also a sufix of patt[0..i]
+void preprocess(string patt) {
+ int i = 1, len = 0;
+
+ while (i < patt.size()) {
+ if (patt[i] == patt[len])
+ table[i++] = ++len;
+ else if (len)
+ len = table[len - 1];
+ else
+ table[i++] = 0;
+ }
+}
+
+// Search for occurrences of patt in txt and add indexes of matches to occurs
+void search(string patt, string txt) {
+ int i = 0, j = 0;
+
+ while (i < txt.size()) {
+ if (patt[j] == txt[i])
+ i++, j++;
+
+ if (j == patt.size()) {
+ occurs.push_back(i - j); // Pattern found at (i - j)
+ j = table[j - 1];
+ } else if (i < txt.size() && patt[j] != txt[i]) {
+ if (j) j = table[j - 1];
+ else i++;
+ }
+ }
+}
--
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