[mintheon] Week 5

best-time-to-buy-and-sell-stock/mintheon.java

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+class Solution {
+  /**
+   시간복잡도: O(n)
+   공간복잡도: O(1)
+   */
+  public int maxProfit(int[] prices) {
+    int buyPrice = prices[0];
+    int maxProfit = 0;
+
+    for(int i = 0; i < prices.length; i++) {
+      buyPrice = Math.min(buyPrice, prices[i]);
+      maxProfit = Math.max(maxProfit, prices[i] - buyPrice);
+    }
+
+    return maxProfit;
+  }
+}

encode-and-decode-strings/mintheon.java

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+import java.util.ArrayList;
+import java.util.List;
+
+public class Codec {
+  String SPLIT = ":";
+
+  // Encodes a list of strings to a single string.
+  public String encode(List<String> strs) {
+    StringBuilder encoded = new StringBuilder();
+
+    for(String str : strs) {
+      encoded.append(str.length()).append(SPLIT).append(str);
+    }
+
+    return encoded.toString();
+  }
+
+  // Decodes a single string to a list of strings.
+  public List<String> decode(String s) {
+    List<String> decoded = new ArrayList<>();
+
+    int pointer = 0;
+    while(pointer < s.length()) {
+      int index = s.indexOf(SPLIT, pointer);
+      int length = Integer.parseInt(s.substring(pointer, index));
+
+      String str = s.substring(index + 1, index + 1 + length);
+      decoded.add(str);
+
+      pointer = index + 1 + length;
+    }
+
+    return decoded;
+  }
+}
+
+// Your Codec object will be instantiated and called as such:
+// Codec codec = new Codec();
+// codec.decode(codec.encode(strs));

group-anagrams/mintheon.java

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+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+class Solution {
+  /**
+   시간복잡도: O(n)
+   공간복잡도: O(n)
+   */
+  public List<List<String>> groupAnagrams(String[] strs) {
+    Map<String, List<String>> anagramMap = new HashMap<>();
+
+    for(String str : strs) {
+      char[] charStr = str.toCharArray();
+      Arrays.sort(charStr);
+      String sortedStr = String.valueOf(charStr);
+
+      if(!anagramMap.containsKey(sortedStr)) {
+        anagramMap.put(sortedStr, new ArrayList<>());
+
+      }
+
+      anagramMap.get(sortedStr).add(str);
+    }
+
+    return new ArrayList<>(anagramMap.values());
+  }
+}