[20250912] BOJ / P5 / 히스토그램 / 이종환

0224LJH/202509/12 BOJ 히스토그램.md

@@ -0,0 +1,105 @@
+```java
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.*;
+
+public class Main {
+
+
+	static int blockCnt;
+	static long ans;
+	static int[] blocks;
+	static PriorityQueue<Block> pq = new PriorityQueue<>();
+	static HashSet<Integer> nums = new HashSet<>();
+	static PriorityQueue<Integer> numPq = new PriorityQueue<>();
+
+	static class Block implements Comparable<Block>{
+		int start;
+		int height;
+
+		public Block (int start, int height) {
+			this.start = start;
+			this.height = height;
+		}
+
+		@Override
+		public int compareTo(Block b) {
+			return Integer.compare(b.height, this.height);
+		}
+	}
+
+
+    public static void main(String[] args) throws NumberFormatException, IOException {
+		init();
+		process();
+		print();
+    }
+
+    public static void init() throws NumberFormatException, IOException {
+    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    	blockCnt = Integer.parseInt(br.readLine());
+    	blocks = new int[blockCnt];
+    	ans = 0;
+    	for (int i = 0; i < blockCnt; i++) {
+    		blocks[i] = Integer.parseInt(br.readLine());
+    		nums.add(blocks[i]);
+    	}
+
+
+    }
+
+    public static void process() { 	
+    	ans = findLargest(0,blockCnt-1);
+
+
+    }
+
+    public static long findLargest(int start, int end) {
+
+    	if (start == end) return blocks[start];
+
+    	int mid = (start+end)/2;
+    	long leftMax = findLargest(start,mid);
+    	long rightMax = findLargest(mid+1,end);
+    	long max = Math.max(leftMax, rightMax);
+
+    	int leftIdx = mid;
+    	int rightIdx = mid+1;
+    	long curNum = Math.min(blocks[leftIdx], blocks[rightIdx]);
+    	long curMax =curNum*(rightIdx-leftIdx+1);
+
+    	while(true) {	
+
+    		if (leftIdx == start && rightIdx == end) break;
+    		int nLeftNum = 0;
+    		int nRightNum = 0;
+    		if (start < leftIdx) nLeftNum = blocks[leftIdx-1];
+    		if (rightIdx < end) nRightNum = blocks[rightIdx+1];
+
+    		if (nLeftNum <= nRightNum && rightIdx != end) {
+    			rightIdx++;
+    		} else {
+    			leftIdx--;
+    		}
+
+    		curNum = Math.min(curNum, blocks[rightIdx]);
+    		curNum = Math.min(curNum, blocks[leftIdx]);
+    		curMax = Math.max(curMax, curNum*(rightIdx-leftIdx+1));
+
+    	}
+
+    	max = Math.max(max, curMax);
+
+    	return max;
+    }
+
+
+
+
+    public static void print() {
+    	System.out.println(ans);
+    }
+}
+```