update: May 12, recursion

daily/May12.cpp

@@ -0,0 +1,42 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution {
+ public:
+  unordered_map<int, int> memo;
+  int minDays(int n) {
+    if (n <= 1) {
+      return n;
+    }
+
+    if (memo.count(n)) {
+      return memo[n];
+    }
+
+    return memo[n] = min(minDays(n / 2) + n % 2, minDays(n / 3) + n % 3) + 1;
+  }
+
+  int minDaysDijkstra(int n) {
+    unordered_map<int, int> dis;
+    priority_queue<pair<int, int>, vector<pair<int, int>>, greater<>> pq;
+    pq.emplace(0, n);
+    while (true) {
+      auto [dx, x] = pq.top();
+      pq.pop();
+      if (x <= 1) {
+        return dx + x;
+      }
+      if (dx > dis[x]) {
+        continue;
+      }
+      for (int d = 2; d <= 3; d++) {
+        int y = x / d;
+        int dy = dx + x % d + 1;
+        if (!dis.count(y) || dy < dis[y]) {
+          dis[y] = dy;
+          pq.emplace(dy, y);
+        }
+      }
+    }
+  }
+};