Solved problems 1077[E, F1] from codeforces

Author: AliOsm

CodeForces/1077E. Thematic Contests.cpp

@@ -0,0 +1,51 @@
+/*
+  Idea:
+    - Try all possible starting values from 1 to `max(a[i])`.
+    - This solution work in ~ `20 * 2*10^5`.
+    - To figure why, the smallest starting number is 1
+      and in each iteration it should be multiplied by 2,
+      so in 18 steps it will reach 262144 which is greater than
+      the number of elements in the array.
+*/
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int const N = 2e5 + 1;
+int n, a[N], fr[N];
+vector<int> all;
+
+int main() {
+  scanf("%d", &n);
+  for(int i = 0; i < n; ++i)
+    scanf("%d", a + i), all.push_back(a[i]);
+
+  sort(all.begin(), all.end());
+  all.resize(unique(all.begin(), all.end()) - all.begin());
+  for(int i = 0; i < n; ++i)
+    a[i] = lower_bound(all.begin(), all.end(), a[i]) - all.begin(),
+    ++fr[a[i]];
+  all.clear();
+
+  for(int i = 0; i < N; ++i)
+    if(fr[i] != 0)
+      all.push_back(fr[i]);
+  sort(all.begin(), all.end());
+
+  int res = 0, tmp, idx, cur;
+  for(int i = 1; i <= all.back(); ++i) {
+    tmp = 0, idx = -1, cur = i;
+    while(true) {
+      idx = lower_bound(all.begin() + idx + 1, all.end(), cur) - all.begin();
+      if(idx == all.size())
+        break;
+      tmp += cur;
+      cur += cur;
+    }
+    res = max(res, tmp);
+  }
+  printf("%d\n", res);
+
+  return 0;
+}

CodeForces/1077F1. Pictures with Kittens (easy version).cpp

@@ -0,0 +1,49 @@
+/*
+  Idea:
+    - Dynamic Programming
+    - dp[idx][prv][rem] represents:
+      idx: the current index
+      prv: how many elements discarded before
+      rem: the remaining elements to take
+*/
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int const N = 2e2 + 1;
+int n, k, x, a[N];
+long long dp[N][N][N];
+
+long long rec(int idx, int prv, int rem) {
+  if(rem < 0 || prv >= k)
+    return -1e15;
+  if(idx == n)
+    return rem == 0 ? 0 : -1e15;
+
+  long long &ret = dp[idx][prv][rem];
+  if(ret != -1)
+    return ret;
+  ret = -1e15;
+
+  ret = max(ret, rec(idx + 1, prv + 1, rem));
+  ret = max(ret, rec(idx + 1, 0, rem - 1) + a[idx]);
+
+  return ret;
+}
+
+int main() {
+  scanf("%d %d %d", &n, &k, &x);
+  for(int i = 0; i < n; ++i)
+    scanf("%d", a + i);
+
+  memset(dp, -1, sizeof dp);
+  long long res = rec(0, 0, x);
+
+  if(res <= 0)
+    puts("-1");
+  else
+    printf("%lld\n", res);
+
+  return 0;
+}

CodeForces/README.md

@@ -575,6 +575,8 @@
 - [1077B. Disturbed People](http://codeforces.com/contest/1077/problem/B)
 - [1077C. Good Array](http://codeforces.com/contest/1077/problem/C)
 - [1077D. Cutting Out](http://codeforces.com/contest/1077/problem/D)
+- [1077E. Thematic Contests](http://codeforces.com/contest/1077/problem/E)
+- [1077F1. Pictures with Kittens (easy version)](http://codeforces.com/contest/1077/problem/F1)
 - [1079A. Kitchen Utensils](http://codeforces.com/contest/1079/problem/A)
 - [1079B. Personalized Cup](http://codeforces.com/contest/1079/problem/B)
 - [1079C. Playing Piano](http://codeforces.com/contest/1079/problem/C)