diff --git a/content/kactl.tex b/content/kactl.tex
index 25beecd..631baa7 100644
--- a/content/kactl.tex
+++ b/content/kactl.tex
@@ -21,6 +21,7 @@
 	\kactlchapter{contest}
 	\kactlchapter{data-structures}
 	\kactlchapter{graph}
+	\kactlchapter{string}
 	\kactlchapter{number-theory}
 	\kactlchapter{geometry}
 	\kactlchapter{math}
diff --git a/content/string/chapter.tex b/content/string/chapter.tex
new file mode 100644
index 0000000..07425a3
--- /dev/null
+++ b/content/string/chapter.tex
@@ -0,0 +1,3 @@
+\chapter{String}
+
+\kactlimport{manacher.cpp}
diff --git a/content/string/manacher.cpp b/content/string/manacher.cpp
new file mode 100644
index 0000000..d7a2a43
--- /dev/null
+++ b/content/string/manacher.cpp
@@ -0,0 +1,52 @@
+/**
+ * Author: me
+ * Description: Find longest palindrome centered at each index.
+ * Initialise with original 0-indexed string. QUERYING IS 1-INDEXED.
+ * Time: $O(N)$
+ */
+
+struct Manacher {
+	string s;
+	vector<int> pl;
+
+	void calc() {
+		int n = s.length() - 1;
+		int l = 0, r = 0;
+
+		for (int i = 1; i <= n; i += 1) {
+			if (i < r) pl[i] = min(r-i, pl[l+r-i]);
+			while (s[i-pl[i]-1] == s[i+pl[i]+1]) pl[i] += 1;
+			if (i + pl[i] > r) {
+				l = i - pl[i];
+				r = i + pl[i];
+			}
+		}
+	}
+
+	Manacher() {}
+	void init(string _s, char f='~') {
+		s = "@"; s += f;
+		for (char c: _s)
+		{s += c; s += f;} s += '|';
+		pl.resize(s.length(), 0);
+		calc();
+	}
+
+	// Query for substring [l, r]
+	// on original string with 1-indexed
+	bool is_palindrome(int l, int r) {
+		l <<= 1; r <<= 1;
+		int mid = (l+r) >> 1;
+		return mid + pl[mid] >= r;
+	}
+};
+/*
+Manacher mana;
+
+void example() {
+	string s;
+	cin >> s;
+	mana.init(s);
+	int l, r; cin >> l >> r;
+	cout << mana.is_palindrome(l, r);
+}*/
diff --git a/kactl.pdf b/kactl.pdf
index 006c6de..73f5cec 100644
Binary files a/kactl.pdf and b/kactl.pdf differ
diff --git a/lab/code b/lab/code
new file mode 100755
index 0000000..a787707
Binary files /dev/null and b/lab/code differ
diff --git a/lab/code.cpp b/lab/code.cpp
new file mode 100644
index 0000000..705bf7e
--- /dev/null
+++ b/lab/code.cpp
@@ -0,0 +1,59 @@
+/**
+ * Author: me
+ * Description: Find longest palindrome centered at each index.
+ * Initialise with original 0-indexed string. QUERYING IS 1-INDEXED.
+ * Time: $O(N)$
+ */
+
+#include <bits/stdc++.h>
+using namespace std;
+
+struct Manacher {
+	string s;
+	vector<int> pl;
+
+	void calc() {
+		int n = s.length() - 1;
+		int l = 0, r = 0;
+
+		for (int i = 1; i <= n; i += 1) {
+			if (i < r) pl[i] = min(r-i, pl[l+r-i]);
+			while (s[i-pl[i]-1] == s[i+pl[i]+1]) pl[i] += 1;
+			if (i + pl[i] > r) {
+				l = i - pl[i];
+				r = i + pl[i];
+			}
+		}
+	}
+
+	Manacher() {}
+	void init(string _s, char f='~') {
+		s = "@"; s += f;
+		for (char c: _s)
+		{s += c; s += f;} s += '|';
+		pl.resize(s.length(), 0);
+		calc();
+	}
+
+	// Query for substring [l, r]
+	// on original string with 1-indexed
+	bool is_palindrome(int l, int r) {
+		l <<= 1; r <<= 1;
+		int mid = (l+r) >> 1;
+		return mid + pl[mid] >= r;
+	}
+};
+
+Manacher mana;
+
+void example() {
+	string s;
+	cin >> s;
+	mana.init(s);
+	int l, r; cin >> l >> r;
+	cout << mana.is_palindrome(l, r);
+}
+
+int main() {
+	example();
+}
diff --git a/lab/sparse_table.cpp b/lab/sparse_table.cpp
deleted file mode 100644
index e5411cb..0000000
--- a/lab/sparse_table.cpp
+++ /dev/null
@@ -1,47 +0,0 @@
-/**
- * Author: me
- * Description: Sparse table for static RMQ.
- * This version is 1-indexed
- * Time: $O(N \log N + Q)$
- */
-
-struct SparseTable {
-	int n;
-	// st[i][j] = min/max in segment len 2^i start at j
-	vector<vector<int>> st;
-	
-	SparseTable() {}
-	void init(int _n, int* a) {
-		n = _n;
-		int lg2 = __lg(n) + 2;
-		st.resize(lg2, vector<int>(n+1));
-		for (int i = 1; i <= n; i += 1) st[0][i] = a[i];
-		
-		for (int i = 1; i < lg2; i += 1)
-		for (int j = 1; j <= n; j += 1)
-		// CAREFUL MIN-MAX
-		st[i][j] = min(st[i-1][j], st[i-1][j + (1 << (i-1))]);
-	}
-	
-	// Query for [l, r]
-	int retrieve(int l, int r) {
-		int i = __lg(r-l+1);
-		//CAREFUL MIN-MAX
-		return min(st[i][l], st[i][r - (1 << i) + 1]);
-	}
-};
-
-/*
-SparseTable rmq;
-
-void example(int n, int q) {
-	int a[n+1];
-	for (int i = 1; i <= n; i += 1) cin >> a[i];
-	rmq.init(n, a);
-	while (q--) {
-		int l, r;
-		cin >> l >> r;
-		cout << rmq.retrieve(l, r) << "\n";
-	}
-}
-*/