[minji-go] Week 1

contains-duplicate/minji-go.java

@@ -0,0 +1,14 @@
+class Solution {
+    public boolean containsDuplicate(int[] nums) {
+        Set<Integer> count = new HashSet<>();
+        boolean answer = false;
+        for(int num : nums){
+            if(count.contains(num)) {
+                answer = true;
+                break;
+            }
+            count.add(num);
+        }
+        return answer;
+    }
+}

house-robber/minji-go.java

@@ -0,0 +1,11 @@
+class Solution {
+    public int rob(int[] nums) {
+        int[] sum = new int[nums.length+1];
+        sum[0] = nums[0];
+        if(nums.length>1) sum[1] = Math.max(nums[0], nums[1]);
+        for(int i=2; i<nums.length; i++){
+            sum[i]=Math.max(nums[i]+sum[i-2],sum[i-1]);
+        }
+        return sum[nums.length-1];
+    }
+}

longest-consecutive-sequence/minji-go.java

@@ -0,0 +1,22 @@
+class Solution {
+    public int longestConsecutive(int[] nums) {
+        Set<Integer> set = new HashSet<>();
+        for(int num: nums) {
+            set.add(num);
+        }
+
+        int answer = 0;
+        for(int num: nums){
+            if(set.contains(num-1)){
+                continue;
+            }
+            int length = 1;
+            while (set.contains(num+length)){
+                length++;
+            }
+            answer = Math.max(answer, length);
+        }
+
+        return answer;
+    }
+}

top-k-frequent-elements/minji-go.java

@@ -0,0 +1,18 @@
+class Solution {
+    public int[] topKFrequent(int[] nums, int k) {
+        Map<Integer, Integer> count = new HashMap<>();
+        for(int num : nums){
+            count.put(num, count.getOrDefault(num, 0)+1);
+        }
+        List<Integer> tops = count.keySet().stream()
+                .sorted((i1, i2) -> count.get(i2)-count.get(i1))
+                .limit(k)
+                .toList();
+
+        int[] answer = new int[k];
+        for(int i=0; i<k; i++) {
+            answer[i] = tops.get(i);
+        }
+        return answer;
+    }
+}

valid-palindrome/minji-go.java

@@ -0,0 +1,15 @@
+class Solution {
+    public boolean isPalindrome(String s) {
+        String regex ="[^A-Za-z0-9]";
+        String palindrome = s.replaceAll(regex,"").toLowerCase();
+
+        boolean answer = true;
+        for(int i=0; i<palindrome.length()/2; i++){
+            if(palindrome.charAt(i) != palindrome.charAt(palindrome.length()-1-i)) {
+                answer = false;
+                break;
+            }
+        }
+        return answer;
+    }
+}