Solve(MST): BOJ 1414 "불우이웃돕기" 문제 풀이

boj/solved/mst/1414/Main.java

@@ -0,0 +1,92 @@
+import java.io.*;
+import java.util.*;
+
+class Main {
+    static int n;
+    static class Node{
+        int start;
+        int end;
+        int w;
+        public Node(int start, int end, int w) {
+            this.start = start;
+            this.end = end;
+            this.w = w;
+        }
+    }
+    static PriorityQueue<Node> nodes = new PriorityQueue<>(Comparator.comparing(a -> a.w));
+    static int[] parents;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        n = Integer.parseInt(br.readLine());
+
+        parents = new int[n+1];
+        for(int i = 0;i<=n;i++) {
+            parents[i] = i;
+        }
+
+        int totalLen = 0;
+        for(int i = 1;i<=n;i++) {
+            char[] tmp = br.readLine().toCharArray();
+            for(int j = 1;j<=n;j++) {
+                if (tmp[j-1] == '0') {
+                    continue;
+                }
+                if (tmp[j-1] >= 'A' && tmp[j-1] <= 'Z') {
+                    int w = (int)(tmp[j-1] - 'A') + 27;
+                    nodes.add(new Node(i, j, w));
+                    totalLen += w;
+                }
+                else {
+                    int w = (int)(tmp[j-1] - 'a' + 1);
+                    nodes.add(new Node(i, j, w));
+                    totalLen += w;
+                }
+            }
+        }
+
+        int res = 0;
+        while(!nodes.isEmpty()) {
+            Node node = nodes.poll();
+            if(find(node.start) == find(node.end)) {
+                continue;
+            }
+            union(node.start, node.end);
+            res += node.w;
+        }
+
+        int tmp = find(1);
+        boolean isConnected = true;
+        for(int i = 2;i<=n;i++) {
+            if (find(i) != tmp) {
+                isConnected = false;
+                break;
+            }
+        }
+
+        if(isConnected) {
+            System.out.println(totalLen - res);
+        }
+        else {
+            System.out.println(-1);
+        }
+    }
+
+    public static int find(int node) {
+        if(parents[node] == node) {
+            return node;
+        }
+        return parents[node] = find(parents[node]);
+    }
+
+    public static void union(int a, int b) {
+        int aParent = find(a);
+        int bParent = find(b);
+
+        parents[aParent] = bParent;
+    }
+}
+
+// 1 : 1 2 3
+// 2 : 4 5 6
+// 3 : 7 8 9