String stuff

Code/suffix_array_test.cpp

+#include <bits/stdc++.h>
+using namespace std;
+
+#define Mod(x,y) (((x)%(y)+(y))%(y))
+#define rep(i, a, b) for(ll (i) = (a); (i) < (b); ++(i))
+#define all(x) begin(x), end(x)
+#define pb push_back
+#define gcd __gcd 
+#define sz(x) (ll)(x.size())
+
+typedef long long ll;
+typedef unsigned long long ull;
+typedef pair<ll, ll> pii;
+typedef vector<ll> vi;
+typedef vector<pii> vii;
+
+const bool debug = false;
+
+struct SuffixArray {
+    vi sa, lcp;
+    SuffixArray(string& s, int lim=256) { // or basic_string<int>
+        int n = sz(s) + 1, k = 0, a, b;
+        vi x(all(s)+1), y(n), ws(max(n, lim)), rank(n);
+        sa = lcp = y, iota(all(sa), 0);
+        for (int j = 0, p = 0; p < n; j = max(1, j * 2), lim = p) {
+            p = j, iota(all(y), n - j);
+            rep(i,0,n) if (sa[i] >= j) y[p++] = sa[i] - j;
+            fill(all(ws), 0);
+            rep(i,0,n) ws[x[i]]++;
+            rep(i,1,lim) ws[i] += ws[i - 1];
+            for (int i = n; i--;) sa[--ws[x[y[i]]]] = y[i];
+            swap(x, y), p = 1, x[sa[0]] = 0;
+            rep(i,1,n) a = sa[i - 1], b = sa[i], x[b] =
+                (y[a] == y[b] && y[a + j] == y[b + j]) ? p - 1 : p++;
+        }
+        rep(i,1,n) rank[sa[i]] = i;
+        for (int i = 0, j; i < n - 1; lcp[rank[i++]] = k)
+            for (k && k--, j = sa[rank[i] - 1];
+                    s[i + k] == s[j + k]; k++);
+    }
+};
+
+string ob_la_di = "DesmondhasabarrowinthemarketplaceMollyisthesingerinabandDesmondsaystoMolly,\"Girl,Ilikeyourface\"AndMollysaysthisasshetakeshimbythehand";
+
+string longest_repeating_substring(string s) {
+    struct SuffixArray suffix_array(s);
+    int i_max, mx = -1;
+    int ind = 0;
+    for (int i : suffix_array.sa) {
+        if (suffix_array.lcp[ind] > mx)
+            i_max = i, mx = suffix_array.lcp[ind];
+        ind++;
+    }
+    return s.substr(i_max, mx);
+}
+
+void solve() {
+    struct SuffixArray suffix_array(ob_la_di);
+    cout << string(ob_la_di.size()+20, '-') << '\n';
+    cout << "Printing the suffix array with associated lcp!\n";
+    cout << "Pattern\n";
+    cout << "lcp\t| suffix\n";
+
+    int ind = 0;
+    for (int i : suffix_array.sa) {
+        cout << suffix_array.lcp[ind] << "\t| " << ob_la_di.substr(i) << endl;
+        ind++;
+    }
+    cout << string(ob_la_di.size()+20, '-') << '\n';
+    
+    cout << "longest repeating substring is:\n";
+    cout << longest_repeating_substring(ob_la_di) << endl;
+} 
+
+
+int main() {
+    ios::sync_with_stdio(0);cin.tie(0);
+    cout << setprecision(15) << fixed;
+
+    solve();
+}
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Code/trie.cpp

+const int SIGMA = 26;
+ 
+typedef struct TrieNode{
+    struct TrieNode *children[SIGMA];
+    bool isEndOfWord;
+} TrieNode;
+ 
+TrieNode* getNode() {
+    TrieNode *node =  new TrieNode;
+    node->isEndOfWord = false;
+    rep(i, 0, SIGMA) node->children[i] = NULL;
+    return node;
+}
+ 
+void insert(TrieNode* root, string key) {
+    TrieNode *node = root;
+ 
+    rep(i, 0, key.size()) {
+        int ind = key[i]-'a';
+        if (!node->children[ind]) node->children[ind] = getNode();
+        node = node->children[ind];
+    }
+ 
+    node->isEndOfWord = true;
+}
+ 
+bool search(TrieNode* root, string key) {
+    TrieNode* node = root;
+ 
+    rep(i, 0, key.size()) {
+        int ind = key[i]-'a';
+        if (!node->children[ind]) return false;
+        node = node->children[ind];
+    }
+ 
+    return node->isEndOfWord;
+}
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