547

Author: lazzzis

547/main.js

@@ -0,0 +1,30 @@
+/**
+ * @param {number[][]} M
+ * @return {number}
+ */
+
+var findCircleNum = function(M) {
+  function find (n) {
+    if (roots[n] === n) return n
+    roots[n] = find(roots[n])
+    return roots[n]
+  }
+  const roots = Array.from(M, (_, i) => i)
+  for (let i = 0, len = M.length; i < len; i++) {
+    for (let j = 0, leng = M[i].length; j < leng; j++) {
+      if (!M[i][j]) continue
+      const ri = find(i)
+      const rj = find(j)
+      roots[ri] = roots[rj] = Math.min(ri, rj)
+    }
+  }
+  for (let i = 0; i < M.length; i++) {
+    roots[i] = find(i)
+  }
+
+  const set = new Set()
+  for (const item of roots) {
+    set.add(item)
+  }
+  return set.size
+};

547/main2.js

@@ -0,0 +1,35 @@
+// https://www.youtube.com/watch?v=TKHIC6muurM
+/**
+ * @param {number[][]} M
+ * @return {number}
+ */
+
+var findCircleNum = function(M) {
+  function dfs (person) {
+    for (let i = 0; i < M[person].length; i++) {
+      if (M[person][i] && !seen.has(i)) {
+        seen.add(i)
+        dfs(i)
+      }
+    }
+  }
+  const seen = new Set()
+  let count = 0
+  for (let i = 0; i < M.length; i++) {
+    if (seen.has(i)) continue
+    seen.add(i)
+    ++count
+    dfs(i)
+  }
+  return count
+};
+
+if (process.env.LZS) {
+  console.log(
+    findCircleNum(
+      [[1,1,0],
+       [1,1,1],
+       [0,1,1]]
+    )
+  )
+}

README.md

@@ -103,6 +103,7 @@
 - [448 Find All Numbers Disappeared in an Array](./448)
 - [495 Teemo Attacking](./495)
 - [532 K-diff Pairs in an Array](./532)
+- [547 Friend Circles](./547)
 - [560 Subarray Sum Equals K](./560)
 - [561 Array Partition I](./561)
 - [565](./565)