✅ greedy

submissions/Codeforces/1883E.cpp

@@ -0,0 +1,82 @@
+#include <bits/stdc++.h>
+using namespace std;
+#ifdef LOCAL
+#include "debug.cpp"
+#else
+#define dbg(...) 42
+#endif
+#define endl '\n'
+#define fastio                      \
+  ios_base::sync_with_stdio(false); \
+  cin.tie(0);                       \
+  cout.tie(0);
+#define len(__x) (int)__x.size()
+using ll = long long;
+using ull = unsigned long long;
+using ld = long double;
+using vll = vector<ll>;
+using pll = pair<ll, ll>;
+using vll2d = vector<vll>;
+using vi = vector<int>;
+using vi2d = vector<vi>;
+using pii = pair<int, int>;
+using vii = vector<pii>;
+using vc = vector<char>;
+#define all(a) a.begin(), a.end()
+#define pb(___x) push_back(___x)
+#define mp(___a, ___b) make_pair(___a, ___b)
+#define eb(___x) emplace_back(___x)
+
+// vector<string> dir({"LU", "U", "RU", "R", "RD", "D",
+// "LD", "L"}); int dx[] = {-1, -1, -1, 0, 1, 1, 1, 0}; int
+// dy[] = {-1, 0, 1, 1, 1, 0, -1, -1};
+vector<string> dir({"U", "R", "D", "L"});
+int dx[] = {-1, 0, 1, 0};
+int dy[] = {0, 1, 0, -1};
+
+const ll oo = 1e18;
+int T(1);
+
+auto solve() {
+  int N;
+  cin >> N;
+
+  vll XS(N);
+  for (auto &xi : XS) cin >> xi;
+
+  ll pm = 0;  // how many moves the previous one did
+  ll ans = 0;
+  for (int i = 1; i < N; i++) {
+    // get how many moves XS[i] need to become equal/greater
+    // to XS[i-1]
+    ll m = 0, tmp = XS[i];
+    while (tmp < XS[i - 1]) m++, tmp *= 2;
+
+    // from those pm movents the previous one did how many
+    // would can we use and keep XS[i-1] less/equal to XS[i]
+    // ?
+    ll tmp2 = XS[i - 1];
+    while (pm and tmp2 * 2 <= tmp) tmp2 *= 2, pm--;
+
+    // the pm movements left make XS[i-1] greater again, so
+    // we will need to use those pm movements left in XS[i]
+    pm = m + pm;
+    ans += pm;
+  }
+
+  cout << ans << endl;
+}
+
+int32_t main(void) {
+#ifndef LOCAL
+  fastio;
+#endif
+
+  cin >> T;
+
+  for (int i = 1; i <= T; i++) {
+    solve();
+  }
+}
+
+// AC, greedy