Create 2127-maximum-employees-to-be-invited-to-a-meeting.js

Author: everthis

2127-maximum-employees-to-be-invited-to-a-meeting.js

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+/**
+ * @param {number[]} favorite
+ * @return {number}
+ */
+var maximumInvitations = function(favorite) {
+  const n = favorite.length, m = Array(n).fill(-1), r = Array.from({ length: n }, () => [])
+  for(let i = 0; i < n; i++) r[favorite[i]].push(i)
+  
+  function dfs(u) {
+    if(m[u] !== -1) return m[u]
+    let res = 0
+    for(let v of r[u]) res = Math.max(res, dfs(v))
+    return m[u] = 1 + res
+  }
+  let res = 0, free = 0
+  for(let i = 0; i < n; ++i) {
+    if (m[i] != -1) continue; // skip visited nodes
+    if (favorite[favorite[i]] == i) {
+      m[i] = m[favorite[i]] = 0;
+      let a = 0, b = 0; // find the length of the longest arms starting from `i` and `A[i]`
+      for (let v of r[i]) {
+          if (v == favorite[i]) continue;
+          a = Math.max(a, dfs(v));
+      }
+      for (let v of r[favorite[i]]) {
+          if (v == i) continue;
+          b = Math.max(b, dfs(v));
+      }
+      free += a + b + 2; // this free component is of length `a+b+2`
+    } 
+  }
+  function dfs2(u) {
+    if (m[u] != -1) return[u, m[u], false]; // this is the merge point
+    m[u] = 0;
+    let [mergePoint, depth, mergePointMet] = dfs2(favorite[u]);
+    if (mergePointMet) { // If we've met the merge point again already, this node is outside of the cycle and should be ignored.
+        m[u] = 0;
+        return [mergePoint, depth, true];
+    }
+    m[u] = 1 + depth; // If we haven't met the merge point, we increment the depth.
+    return [mergePoint, m[u], u == mergePoint];
+  }
+  
+  for(let i = 0; i < n; i++) {
+    if(m[i] !== -1) continue
+    let [mergePoint, depth, mergePointMet] = dfs2(i)
+    if(mergePointMet) res = Math.max(res, depth)
+  }
+  
+  return Math.max(res, free)
+};
+