[Hyeri1ee] WEEK 04 Solutions

find-minimum-in-rotated-sorted-array/Hyeri1ee.java

@@ -0,0 +1,11 @@
+//맨뒤 요소 맨앞으로
+import java.util.*;
+
+
+class Solution {
+    public int findMin(int[] nums) {
+        Arrays.sort(nums);
+        return nums[0];
+    }
+}
+

maximum-depth-of-binary-tree/Hyeri1ee.java

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+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+ import java.util.*;
+class Solution {
+    private static int solve(TreeNode root, int depth){
+        if (root == null){
+            return depth;
+        }
+
+        //root가null이 아닌 경우
+        return Math.max(solve(root.left, depth+1) , solve(root.right, depth+1));
+
+    }
+    public int maxDepth(TreeNode root) {
+        int result = solve(root, 0);
+        return result;
+    }
+}
+

merge-two-sorted-lists/Hyeri1ee.java

@@ -0,0 +1,37 @@
+import java.util.*;
+
+
+
+
+class Solution {
+
+
+    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
+        ListNode merged = new ListNode();//머지 된 노드 모음
+        ListNode temp = merged;
+        while(list1 != null && list2 != null){
+
+            ListNode newNode = new ListNode();//새로운 노드
+            if (list1.val > list2.val){
+                //list2
+                newNode.val = list2.val;
+                list2 =list2.next;//다음 가리키도록\
+               // merged.next
+            }else{
+                newNode.val =list1.val;
+                list1=list1.next;//다음 가리키도록
+            }
+
+            merged.next = newNode;
+            merged =merged.next;
+
+        }        
+
+        if (list1==null)
+            merged.next= list2;
+        else if (list2 == null)
+            merged.next=list1;
+
+        return temp.next;
+    }
+}

word-search/Hyeri1ee.java

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+import java.util.*;
+
+
+class Solution {
+
+    //상,하,좌,우
+    static int[] dx = {0,1,-1,0};
+    static int[] dy = {1,0,0,-1};
+
+    static int m, n;
+
+    static boolean result; //exist 함수가 호출될때마다 초기화해야함
+    static char[][] map; //지역변수 board 저장용
+    static String w; //word 저장용
+    public boolean exist(char[][] board, String word) {
+
+        result=false;
+
+        m = board.length;
+        n = board[0].length;
+
+        w = word;
+        //map <- board
+        map = new char[m][n];
+        for(int i =0; i<m;i++){
+            for(int j=0; j< n; j++){
+                map[i][j] = board[i][j];
+            }
+        }
+
+
+        for(int x =0 ; x < m; x++){
+            for(int y =0 ; y < n ;y++){
+                dfs(x, y , 0); //위치 x,y, word에 대한 찾는 인덱스
+                if (result) return result;
+            }
+        }
+
+
+
+        //기본 
+        return result;
+    }
+
+    private static void dfs(int x, int y, int idx){
+        //종료조건
+        if (result) return;
+
+        if (!checkin(x, y) || map[x][y] != w.charAt(idx)) return;
+
+        //마지막 문자일때 종료
+        if (idx == w.length() - 1){
+            result = true;
+            return;
+        }   
+
+        char temp = map[x][y];
+        map[x][y] = '#';
+
+        for(int i = 0; i < 4; i++){
+            dfs(x + dx[i], y + dy[i], idx + 1);
+        }
+
+        map[x][y] = temp;
+
+    }
+
+    //map 내부 checkin 함수 정의
+    private static boolean checkin(int x, int y){
+        return x >= 0 && x < m && y >= 0 && y < n;
+    }
+}
+