leetcode

commit d5a8b6d70876bf6a425db8703344d97dafbd7b5e
parent 8a1900f1c2c4c261b35096e570a6035dcd966a49
Author: Dimitrije Dobrota <mail@dimitrijedobrota.com>
Date:   Wed,  1 Feb 2023 00:35:52 +0100

Dynamic Programming I: Day 11

Diffstat:
A
Problems/0096.cpp
 | 
11
+++++++++++
A
Problems/0264.cpp
 | 
41
+++++++++++++++++++++++++++++++++++++++++
M
README.md
 | 
2
++

3 files changed, 54 insertions(+), 0 deletions(-)
diff --git a/Problems/0096.cpp b/Problems/0096.cpp
@@ -0,0 +1,11 @@
+class Solution {
+public:
+  int numTrees(int n) {
+    vector<int> dp(n + 1);
+    dp[0] = dp[1] = 1;
+
+    for (int i = 2; i <= n; i++)
+      for (int j = 1; j <= i; j++) dp[i] += dp[j - 1] * dp[i - j];
+    return dp.back();
+  }
+};
diff --git a/Problems/0264.cpp b/Problems/0264.cpp
@@ -0,0 +1,41 @@
+// Brute force solution
+class Solution {
+public:
+  int nthUglyNumber(int n) {
+    priority_queue<long long, vector<long long>, greater<long long>> pq;
+    unordered_set<long long> us;
+    int count;
+
+    pq.push(1);
+    count = 1;
+    while (!pq.empty() && count < n) {
+      long long n = pq.top();
+      pq.pop();
+      for (int i : {2, 3, 5}) {
+        if (us.count(n * i)) continue;
+        pq.push(n * i);
+        us.insert(n * i);
+      }
+      count++;
+    }
+
+    return (int)pq.top();
+  }
+};
+
+// DP solution
+class Solution {
+public:
+  int nthUglyNumber(int n) {
+    vector<int> k(n);
+    k[0] = 1;
+    int t2 = 0, t3 = 0, t5 = 0;
+    for (int i = 1; i < n; i++) {
+      k[i] = min(k[t2] * 2, min(k[t3] * 3, k[t5] * 5));
+      t2 += k[i] == k[t2] * 2;
+      t3 += k[i] == k[t3] * 3;
+      t5 += k[i] == k[t5] * 5;
+    }
+    return k.back();
+  }
+};
diff --git a/README.md b/README.md
@@ -67,6 +67,7 @@ for solving problems.
 |  0091  |   Medium   | [Decode Ways](Problems/0091.cpp)                                                                 |
 |  0093  |   Medium   | [Restore IP Addresses](Problems/0093.cpp)                                                        |
 |  0094  |    Easy    | [Binary Tree Inorder Traversal](Problems/0094.cpp)                                               |
+|  0096  |   Medium   | [Unique Binary Search Trees](Problems/0096.cpp)                                                  |
 |  0098  |   Medium   | [Validate Binary Search Tree](Problems/0098.cpp)                                                 |
 |  0099  |   Medium   | [Recover Binary Search Tree](Problems/0099.cpp)                                                  |
 |  0100  |    Easy    | [Same Tree](Problems/0100.cpp)                                                                   |
@@ -141,6 +142,7 @@ for solving problems.
 |  0242  |    Easy    | [Valid Anagram](Problems/0242.cpp)                                                               |
 |  0257  |    Easy    | [Binary Tree Paths](Problems/0257.cpp)                                                           |
 |  0263  |    Easy    | [Ugly Number](Problems/0263.cpp)                                                                 |
+|  0264  |   Medium   | [Ugly Number II](Problems/0264.cpp)                                                              |
 |  0278  |    Easy    | [First Bad Version](Problems/0278.cpp)                                                           |
 |  0279  |   Medium   | [Perfect Squares](Problems/0279.cpp)                                                             |
 |  0283  |    Easy    | [Move Zeroes](Problems/0283.cpp)                                                                 |