Merge pull request #2423 from Hyeri1ee/main

[Hyeri1ee] WEEK 02 Solutions

Author: OstenHun

climbing-stairs/Hyeri1ee.java

@@ -0,0 +1,28 @@
+import java.util.*;
+
+class Solution {
+    public int climbStairs(int n) {
+        int[] steps = new int[n+1];
+        if (n == 1) return 1;
+        if (n == 2) return 2;
+        if (n == 3) return 3;
+        steps[1] = 1; steps[2] = 2;//2, 1+1
+        steps[3] = 3;
+        for(int i = 4;i < n+1; i++){
+            steps[i] = steps[i-1] + steps[i-2];
+        }
+        /*
+        steps[4] = 
+        1+1+1+1
+        1+2+1
+        2+2
+        2+1+1
+        1+1+2
+        */
+
+        return steps[n];
+        
+
+    }
+}
+

longest-consecutive-sequence/Hyeri1ee.java

@@ -0,0 +1,55 @@
+import java.util.*;
+
+class Solution {
+    public int longestConsecutive(int[] nums) {
+        //int[] 를 정렬
+        Arrays.sort(nums);
+        //maxlength를 갱신하는 식으로 
+        int maxLength = 0;
+        int curLength = 0 ;
+        long prev = Long.MIN_VALUE;
+        long cur = Long.MIN_VALUE;
+
+
+        for(int i =0 ; i < nums.length; i++){
+
+            //공통
+            prev = cur;
+            cur = nums[i];
+            System.out.println("i: "+ i);
+
+            //System.out.println("cur: "+ cur);
+            //System.out.println("prev: "+ prev);
+            if (curLength == 0) curLength++;
+
+            if (cur == prev + 1){
+                    curLength++;
+                    maxLength = Math.max(maxLength, curLength);
+                    //System.out.println("curLength : " + curLength);
+                    //System.out.println("maxLength : " + maxLength);
+            }else{//다르면 
+                    System.out.println("여기");
+                    
+
+                    if (cur == prev){
+                        maxLength = Math.max(maxLength, curLength);
+                    }else{
+                        maxLength = Math.max(maxLength, curLength);
+                        curLength = 0;
+                    }
+
+                    //System.out.println("curLength : " + curLength);
+                    //System.out.println("maxLength : " + maxLength);
+            }
+
+
+        
+
+
+            
+        }
+
+        return maxLength;
+        
+    }
+}

top-k-frequent-elements/Hyeri1ee.java

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+import java.util.*;
+
+class Solution {
+    public int[] topKFrequent(int[] nums, int k) {
+        HashMap<Integer, Integer> maps = new HashMap<>(); //nums[i] 대상, 등장 횟수
+        
+            for(int i =0; i <nums.length; i++){
+                maps.put(nums[i], maps.getOrDefault(nums[i], 0) + 1);
+            }
+        
+
+
+        ArrayList<Integer> list = new ArrayList<>();
+        //maps를 value기준으로 내림차순 정렬후, list에 k개만큼만 key값 추가
+        Map<Integer, Integer> sorts = 
+            maps.entrySet()
+            .stream()
+            .sorted(Map.Entry.<Integer, Integer>comparingByValue().reversed())
+            .limit(k)
+            .collect(Collectors.toMap(
+                Map.Entry::getKey,
+                Map.Entry::getValue,
+                (a, b) -> a,
+                LinkedHashMap::new
+            ));
+
+        for(int t : sorts.keySet()){
+            list.add(t);
+        }
+
+        return list.stream()
+                .mapToInt(Integer::intValue)
+                .toArray();
+
+            //list.stream().mapToInt(Integer::intValue).toArray(); 
+            //Arrays.stream(arr).boxed().toList();
+    }
+}

valid-anagram/Hyeri1ee.java

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+import java.util.*;
+
+class Solution {
+    public boolean isAnagram(String s, String t) {
+        if (s.length() != t.length()) return false;
+
+        //s를 hashmap에 저장하고, t에서 하나씩 없애기
+        HashMap<Character, Integer> maps = new HashMap<>();
+
+        for(int i =0 ; i < s.length(); i++){
+            char c = s.charAt(i);
+
+            if (maps.containsKey(c)) maps.put(c, maps.get(c)+1);
+            else maps.put(c, 1);
+                
+        }
+
+        for(int i = 0; i< t.length() ;i++){
+            char c = t.charAt(i);
+            if (maps.containsKey(c)){
+                if (maps.get(c) > 1) maps.put(c, maps.get(c) - 1);
+                else maps.remove(c);
+            }
+        }
+
+
+        if (maps.size() == 0) return true;
+
+        return false;
+       
+
+        
+    }
+}