solve: 프로그래머스 문제 풀이 - 4일차

Author: OhChangEun

2025-08-16/오창은/[solved] 프로그래머스_k진수에서 소수 개수 구하기.java

@@ -0,0 +1,44 @@
+import java.util.*;
+
+class Solution {
+    boolean isPrime(long num) {
+        if (num < 2) return false;
+        for (long i = 2; i * i <= num; i++) {
+            if (num % i == 0) return false;
+        }
+        return true;
+    }
+
+    public int solution(int n, int k) {
+        String numInBaseK = Integer.toString(n, k); // k진수 변환
+
+        List<String> list = new ArrayList<>();
+        StringBuilder sb = new StringBuilder();
+
+        for (char ch : numInBaseK.toCharArray()) {
+            if (ch == '0') {
+                if (sb.length() > 0) {
+                    String res = sb.toString();
+                    long value = Long.parseLong(res); // ← long으로 변환
+                    if (isPrime(value)) {
+                        list.add(res);
+                    }
+                    sb = new StringBuilder();
+                }
+            } else {
+                sb.append(ch);
+            }
+        }
+
+        // 마지막 처리
+        if (sb.length() > 0) {
+            String res = sb.toString();
+            long value = Long.parseLong(res);
+            if (isPrime(value)) {
+                list.add(res);
+            }
+        }
+
+        return list.size();
+    }
+}

2025-08-16/오창은/[solved] 프로그래머스_모음 사전.java

@@ -0,0 +1,29 @@
+import java.util.*;
+
+class Solution {
+    String[] words = { "A", "E", "I", "O", "U" };
+    int maxSize = words.length;
+    List<String> dictionary = new ArrayList<>();
+    
+    public int solution(String word) {
+        backtrack("", 0);
+        
+        int answer = dictionary.indexOf(word) + 1;
+        return answer;
+    }
+    
+    public void backtrack(String curr, int depth) {
+        if (depth > 0) {
+            dictionary.add(curr);
+            // System.out.println(curr);
+        }
+        
+        if (depth == maxSize) {
+            return;
+        }
+  
+        for (String word: words) {
+        	backtrack(curr + word, depth + 1);
+        }
+    }
+}

2025-08-16/오창은/[solved] 프로그래머스_보석 쇼핑.java

@@ -0,0 +1,46 @@
+import java.util.*;
+
+class Solution {
+    public int[] solution(String[] gems) {
+        int[] answer = {};
+      
+        Map<String, Integer> gemsMap = new HashMap<>();
+        for (String gem: gems) {
+        	gemsMap.put(gem, gemsMap.getOrDefault(gem, 0) + 1);    
+        }
+        
+        //System.out.println(gemsMap);
+        int totalGemsCounts = gemsMap.size(); // 보석 종류
+        
+        int[] min = {0, gems.length-1};
+        int left = 0;
+        int right = 0;
+        Map<String, Integer> currMap = new HashMap<>();
+
+        for (right = 0; right < gems.length; right++) {
+           	String gem = gems[right]; 
+            currMap.put(gem, currMap.getOrDefault(gem, 0) + 1);
+            // System.out.println(currMap);
+            
+            // 필요한 보석 종류가 됐으면 왼쪽 포인터 이동
+            while (currMap.size() >= totalGemsCounts) {                        
+                // System.out.println(right + " " + left);
+                if (right - left < min[1] - min[0]) {
+                    min[1] = right; // 1-based
+                    min[0] = left;
+                }
+                
+           		String removeGem = gems[left];	
+                currMap.put(removeGem, currMap.getOrDefault(removeGem, 0) - 1);
+                if (currMap.get(removeGem) == 0) {
+                    currMap.remove(removeGem);
+                }
+            	// System.out.println(currMap);
+                left++;
+            }
+
+        }
+        
+        return new int[] { min[0] + 1, min[1] + 1};
+    }
+}