feat: add UFDS flashcards and project learnings infrastructure

org/cpp/dsa/udfs.org

@@ -0,0 +1,41 @@
+#+title: Udfs
+* impl
+#+begin_src cpp
+#include <vector>
+#include <numeric>
+#include <algorithm>
+class Ufs {
+  private:
+  std::vector<int> p;
+  std::vector<int> s;
+  std::vector<int> r;
+  public:
+  Ufds(int n) {
+    p.resize(n);
+    std::iota(p.begin(), p.end(), 0);
+    s.assign(n, 1); // test on equality with the assign fill and iota explain the difference
+    std::fill(r.begin(),r.end(),0);
+    numSets = n;
+  }
+  ~Ufds() {}
+  ~Ufds() = default;
+  int find(int x) {
+    if (p[x] == x) return x;
+    return p[x] = find(p[x]);
+  }
+  int find(int x) {
+    int px = p[x];
+    if (px != x) {
+      px = find(px);
+    }
+    p[x] = px;
+    return px;
+  }
+};
+#+end_src
+
+should ask what new returns? delete? what happens? why are we deleting it ? heap allocated?
+should show equivalent version of using std::array to vector
+should ask what resize does?
+
+what about a true dynammic version where we create it upon calling find()