[hjeomdev] WEEK 14 Solutions

counting-bits/hjeomdev.java

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+class Solution {
+    public int[] countBits(int n) {
+        // 0 ~ n 까지 2진수를 구하고, 그 수의 모든 자릿값의 합을 구해야함
+
+        int[] result = new int[n + 1];
+
+        for (int i = 0; i <= n; i++) {
+            String binaryString = Integer.toBinaryString(i);
+            int sum = 0;
+            for (int j = 0 ; j < binaryString.length(); j++) {
+                sum += binaryString.charAt(j) - '0';
+            }
+            result[i] = sum;
+        }
+
+        return result;
+    }
+}

reverse-bits/hjeomdev.java

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+class Solution {
+    public int reverseBits(int n) {
+        String origin = Integer.toBinaryString(n);
+        origin = String.format("%32s", origin).replace(' ', '0');
+        String reversed = "";
+        for (int i = origin.length() - 1; i >= 0; i--) {
+            reversed += origin.charAt(i);
+        }
+        // System.out.println(origin);
+        // System.out.println(reversed);
+        int result = Integer.parseInt(reversed, 2);
+        // System.out.println(result);
+        return result;
+    }
+}