[chjung99] WEEK 12 solutions

palindromic-substrings/chjung99.go

@@ -0,0 +1,24 @@
+func countSubstrings(s string) int {
+    ans := 0
+    n := len(s)
+
+    for i := 0; i < n; i++ {
+        for j := i+1; j <= n; j++ {
+            if (isPalindrom(s[i:j])) {
+                ans++
+            }
+        }
+    }
+    return ans
+}
+
+func isPalindrom(s string) bool {
+    var rev []byte
+    n := len(s)
+    for i := n-1; i >= 0; i-- {
+        rev = append(rev, s[i])
+    }
+    return string(rev) == s
+}
+
+

sum-of-two-integers/chjung99.go

@@ -0,0 +1,12 @@
+func getSum(a int, b int) int {
+    for b != 0 {
+        sumWithoutCarry := a ^ b
+        carry := (a & b) << 1
+
+        a = sumWithoutCarry
+        b = carry
+    }
+    return a
+}
+
+

top-k-frequent-elements/chjung99.java

@@ -0,0 +1,34 @@
+class Solution {
+    public int[] topKFrequent(int[] nums, int k) {
+        Map<Integer, Integer> map = new HashMap<>();
+        int[] answer = new int[k];
+        int n = nums.length;
+        List<Data> result = new ArrayList<>();
+
+        for (int i = 0; i < n; i++) {
+            int key = nums[i];
+            if (map.get(key) == null) {
+                map.put(key, 1);
+            } else {
+                map.put(key, map.get(key) + 1);
+            }
+        }
+        for (int key: map.keySet()) {
+            result.add(new Data(key, map.get(key)));
+        }
+        result.sort((a, b) -> b.count() - a.count());
+
+        for (int i = 0; i < k; i++) {
+            answer[i] = result.get(i).key();
+        }
+
+        return answer;
+
+    }
+    record Data(
+            int key,
+            int count
+    ){}
+}
+
+