260105 : [BOJ 2655] 가장 높은 탑쌓기

_youngman/가장높은탑쌓기.java

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+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    static class Brick {
+        int area, height, weight, idx;
+        Brick(int area, int height, int weight, int idx) {
+            this.area = area;
+            this.height = height;
+            this.weight = weight;
+            this.idx = idx;
+        }
+    }
+
+    public static void main(String[] args) throws Exception {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        int N = Integer.parseInt(br.readLine());
+
+        Brick[] bricks = new Brick[N];
+        for (int i = 0; i < N; i++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            int area = Integer.parseInt(st.nextToken());
+            int height = Integer.parseInt(st.nextToken());
+            int weight = Integer.parseInt(st.nextToken());
+            bricks[i] = new Brick(area, height, weight, i + 1);
+        }
+
+        // 1. 밑면 넓이 내림차순 정렬
+        Arrays.sort(bricks, (a, b) -> b.area - a.area);
+
+        int[] dp = new int[N];
+        int[] prev = new int[N];
+        Arrays.fill(prev, -1);
+
+        int maxHeight = 0;
+        int lastIdx = 0;
+
+        // 2. DP
+        for (int i = 0; i < N; i++) {
+            dp[i] = bricks[i].height;
+            for (int j = 0; j < i; j++) {
+                if (bricks[j].weight > bricks[i].weight) {
+                    if (dp[j] + bricks[i].height > dp[i]) {
+                        dp[i] = dp[j] + bricks[i].height;
+                        prev[i] = j;
+                    }
+                }
+            }
+            if (dp[i] > maxHeight) {
+                maxHeight = dp[i];
+                lastIdx = i;
+            }
+        }
+
+        // 3. 역추적
+        List<Integer> result = new ArrayList<>();
+        while (lastIdx != -1) {
+            result.add(bricks[lastIdx].idx);
+            lastIdx = prev[lastIdx];
+        }
+
+        // 출력
+        System.out.println(result.size());
+        for (int i = 0; i < result.size(); i++) {
+            System.out.println(result.get(i));
+        }
+    }
+}