Weekly Contest 101

Author: MaskRay

numbers-at-most-n-given-digit-set.cc

@@ -0,0 +1,24 @@
+// Numbers At Most N Given Digit Set
+#define ALL(x) (x).begin(), (x).end()
+
+class Solution {
+public:
+  int atMostNGivenDigitSet(vector<string>& D, int N) {
+    long c = 1, r = 0, s = 0, ss = 1;
+    vector<int> ds;
+    transform(ALL(D), back_inserter(ds), [](auto& x) { return stoi(x); });
+    for(;;) {
+      int n = N%10;
+      s = 0;
+      for (int d: ds)
+        if (d < n)
+          s += c;
+        else if (d == n)
+          s += ss;
+      ss = s;
+      if (!(N /= 10)) break;
+      r += c *= ds.size();
+    }
+    return s+r;
+  }
+};

online-stock-span.cc

@@ -0,0 +1,13 @@
+// Online Stock Span
+class StockSpanner {
+  vector<pair<int, int>> s;
+public:
+  StockSpanner() {}
+  int next(int price) {
+    int w = 1;
+    for (; s.size() && s.back().first <= price; s.pop_back())
+      w += s.back().second;
+    s.emplace_back(price, w);
+    return w;
+  }
+};

rle-iterator.cc

@@ -0,0 +1,18 @@
+// RLE Iterator
+class RLEIterator {
+  vector<int> A;
+  int i = 0, c = 0;
+public:
+  RLEIterator(vector<int> A) : A(A) {}
+
+  int next(int n) {
+    while (i < A.size()) {
+      if ((c += n) <= A[i])
+        return A[i+1];
+      n = c-A[i];
+      c = 0;
+      i += 2;
+    }
+    return -1;
+  }
+};

valid-permutations-for-di-sequence.cc

@@ -0,0 +1,27 @@
+// Valid Permutations for DI Sequence
+#define FOR(i, a, b) for (remove_cv<remove_reference<decltype(b)>::type>::type i = (a); i < (b); i++)
+#define REP(i, n) FOR(i, 0, n)
+#define ROF(i, a, b) for (remove_cv<remove_reference<decltype(b)>::type>::type i = (b); --i >= (a); )
+
+class Solution {
+  static const int P = 1000000007;
+public:
+  int numPermsDISequence(string S) {
+    int n = S.size();
+    vector<int> f(n+1);
+    f[0] = 1;
+    REP(i, n)
+      if (S[i] == 'D')
+        ROF(j, 0, i)
+          (f[j] += f[j+1]) %= P;
+      else {
+        int s = 0;
+        REP(j, i+2) {
+          int g = f[j];
+          f[j] = s;
+          (s += g) %= P;
+        }
+      }
+    return accumulate(f.begin(), f.end(), 0L) % P;
+  }
+};