Create 547.cpp

LeetCode/547.cpp

@@ -0,0 +1,75 @@
+
+class DisjointSet
+{
+public:
+    int* parent;
+    int countRoot;
+
+    DisjointSet(int size) {
+        parent = new int[size];
+        memset(parent, 0xFF, sizeof(int) * size);
+        countRoot = 0;
+    }
+
+    ~DisjointSet() {
+        delete[] parent;
+    }
+
+    int find(int id) {
+        if (parent[id] != -1 && parent[id] != id) {
+            parent[id] = find(parent[id]);
+        }
+
+        // printf("parent of %d is %d\n", id, parent[id]);
+        return parent[id];
+    }
+
+    void setParent(int child, int upper) {
+        if (upper == child) {
+            parent[child] = child;
+            countRoot++;
+        }
+        else {
+            if (parent[child] == -1) {
+                parent[child] = child;
+                countRoot++;
+            }
+            if (parent[upper] == -1) {
+                parent[upper] = upper;
+                countRoot++;
+            }
+
+            int childRoot = find(child);
+            int upperRoot = find(upper);
+            if (childRoot != upperRoot) countRoot--;
+
+            // printf("set parent of %d to %d\n", childRoot, upperRoot);
+            parent[childRoot] = upperRoot;
+        }
+    }
+};
+
+class Solution {
+public:
+    int findCircleNum(vector<vector<int>>& isConnected) {
+        int n = isConnected.size();
+        DisjointSet dset(n);
+        for (int i = 0; i < n; i++)
+        {
+            dset.setParent(i, i);
+        }
+
+        for (int i = 0; i < n; i++)
+        {
+            for (int j = 0; j < n; j++) {
+                if (i == j) continue;
+
+                if (isConnected[i][j]) {
+                    dset.setParent(i, j);
+                }
+            }
+        }
+
+        return dset.countRoot;
+    }
+};