1 files changed, 38 insertions, 0 deletions
diff --git a/content/string/suffixArray.cpp b/content/string/suffixArray.cpp
new file mode 100644
index 0000000..8b698d2
--- /dev/null
+++ b/content/string/suffixArray.cpp
@@ -0,0 +1,38 @@
+constexpr int MAX_CHAR = 256;
+struct SuffixArray {
+	int n;
+	vector<int> SA, LCP;
+	vector<vector<int>> P;
+
+	SuffixArray(const string& s) : n(sz(s)), SA(n), LCP(n),
+		P(__lg(2 * n - 1) + 1, vector<int>(n)) {
+		P[0].assign(all(s));
+		iota(all(SA), 0);
+		sort(all(SA), [&](int a, int b) {return s[a] < s[b];});
+		vector<int> x(n);
+		for (int k = 1, c = 1; c < n; k++, c *= 2) {
+			iota(all(x), n - c);
+			for (int ptr = c; int i : SA) if (i >= c) x[ptr++] = i - c;
+
+			vector<int> cnt(k == 1 ? MAX_CHAR : n);
+			for (int i : P[k-1]) cnt[i]++;
+			partial_sum(all(cnt), begin(cnt));
+			for (int i : x | views::reverse) SA[--cnt[P[k-1][i]]] = i;
+
+			auto p = [&](int i) {return i < n ? P[k-1][i] : -1;};
+			for (int i = 1; i < n; i++) {
+				int a = SA[i-1], b = SA[i];
+				P[k][b] = P[k][a] + (p(a) != p(b) || p(a+c) != p(b+c));
+		}}
+		for (int i = 1; i < n; i++) LCP[i] = lcp(SA[i-1], SA[i]);
+	}
+
+	int lcp(int x, int y) {//x & y are text-indices, not SA-indices
+		if (x == y) return n - x;
+		int res = 0;
+		for (int i = sz(P) - 1; i >= 0 && max(x, y) + res < n; i--) {
+			if (P[i][x + res] == P[i][y + res]) res |= 1 << i;
+		}
+		return res;
+	}
+};