833B - The Bakery

https://codeforces.com/problemset/submission/833/173637014

Codeforces/833/B/B.cpp

@@ -0,0 +1,138 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 35005,
+          K = 55;
+
+template <typename T>
+class SegmentTree {
+  private:
+    struct node {
+        int l, r;
+        T m, d;
+        node *lchild, *rchild;
+
+        node(int _l = 0, int _r = 0)
+            : l(_l),
+              r(_r),
+              m(0),
+              d(0),
+              lchild(nullptr),
+              rchild(nullptr) {}
+
+        ~node() {
+            delete lchild;
+            delete rchild;
+        }
+
+        void pushup() {
+            m = 0;
+            if (lchild) m = std::max(m, lchild->m);
+            if (rchild) m = std::max(m, rchild->m);
+        }
+
+        void pushdown() {
+            if (!d) return;
+
+            lchild->d += d;
+            rchild->d += d;
+
+            lchild->m += d;
+            rchild->m += d;
+
+            d = 0;
+        }
+    };
+
+    void build(node *&u, int l, int r) {
+        u = new node(l, r);
+
+        if (l == r) return;
+
+        int mid = l + r >> 1;
+        build(u->lchild, l, mid);
+        build(u->rchild, mid + 1, r);
+    }
+
+    void modify(node *u, int l, int r, T v) {
+        if (l <= u->l && u->r <= r) {
+            u->d += v;
+            u->m += v;
+
+            return;
+        }
+
+        u->pushdown();
+
+        int mid = u->l + u->r >> 1;
+        if (l <= mid) modify(u->lchild, l, r, v);
+        if (r > mid) modify(u->rchild, l, r, v);
+
+        u->pushup();
+    }
+
+    T query(node *u, int l, int r) {
+        if (l <= u->l && u->r <= r) return u->m;
+
+        u->pushdown();
+
+        int mid = u->l + u->r >> 1;
+        T res = 0;
+        if (l <= mid) res = std::max(res, query(u->lchild, l, r));
+        if (r > mid) res = std::max(res, query(u->rchild, l, r));
+
+        return res;
+    }
+
+    node *root;
+
+  public:
+    SegmentTree(int n)
+        : root(nullptr) {
+        build(root, 1, n);
+    }
+
+    void modify(int l, int r, T v) {
+        modify(root, l, r, v);
+    }
+
+    T query(int l, int r) {
+        return query(root, l, r);
+    }
+};
+
+int n, k, a[N], pre[N], pos[N], f[K][N];
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> k;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i];
+
+        pre[i] = pos[a[i]];
+        pos[a[i]] = i;
+    }
+
+    for (int i = 1; i <= k; i++) {
+        SegmentTree<int> tr(n);
+
+        for (int j = 1; j <= n; j++) {
+            tr.modify(j, j, f[i - 1][j - 1]);
+        }
+
+        for (int j = 1; j <= n; j++) {
+            tr.modify(pre[j] + 1, j, 1);
+            f[i][j] = tr.query(i, j);
+        }
+    }
+
+    cout << f[k][n] << endl;
+
+    return 0;
+}