java/programmers/src/level3/kakao/kakao2019/징검다리건너기.java

programmers/java/src/level3/kakao/kakao2019/징검다리건너기.java

@@ -0,0 +1,70 @@
+package level3.kakao.kakao2019;
+
+import java.util.ArrayDeque;
+import java.util.Arrays;
+
+//https://school.programmers.co.kr/learn/courses/30/lessons/64062
+public class 징검다리건너기 {
+
+    // soultion1 : 이분탐색 이용
+    public int solution1(int[] stones, int k) {
+        int start = 1;
+        int end = Math.max(stones.length, Arrays.stream(stones).max().getAsInt());
+        int answer = 1;
+
+        while(start <= end) {
+            int mid = (start + end) / 2;
+            if(check(stones, mid, k)) {
+                answer = Math.max(answer, mid);
+                start = mid + 1;
+            } else {
+                end = mid - 1;
+            }
+        }
+        return answer;
+    }
+
+    private boolean check(int[] stones, int m, int k) {
+        int cnt = 0;
+        for(int stone : stones) {
+            if(stone < m) {
+                cnt += 1;
+            } else {
+                cnt = 0;
+            }
+
+            if(cnt == k) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    // soultion2 : 슬라이딩 윈도우, deque 사용
+    public int solution2(int[] stones, int k) {
+        ArrayDeque<Integer> q = new ArrayDeque<>();
+        int answer = 200000000;
+
+        for(int i=0; i<stones.length; i++) {
+            if( (!q.isEmpty()) && (q.peekFirst() == (i - k))) {
+                q.pollFirst();
+            }
+
+            while(!q.isEmpty()) {
+                if(stones[q.peekLast()] < stones[i]) {
+                    q.pollLast();
+                } else {
+                    break;
+                }
+            }
+
+            q.offerLast(i);
+            if(i >= (k-1)) {
+                answer = Math.min(answer, stones[q.peekFirst()]);
+            }
+        }
+        return answer;
+    }
+
+
+}