number-of-1-bits solution

Author: togo26

number-of-1-bits/togo26.js

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+/**
+ * @param {number} n
+ * @return {number}
+ */
+
+// 31 비트 범위는 상수로 취급
+
+// Log-based calculation
+// TC: O(1)  / SC: O(1)
+// 비트 제약이 없을 경우 -> TC: O(logn) / SC: O(logn)
+var hammingWeight = function (n) {
+  const BIT_RANGE = 31;
+  let bits = Array.from({ length: BIT_RANGE }).fill(0);
+
+  let remainder = n;
+  while (remainder > 0) {
+    const exp = Math.min(Math.floor(Math.log2(remainder)), BIT_RANGE - 1);
+    bits[exp] = true;
+    const value = remainder <= 1 ? 1 : Math.pow(2, exp);
+    remainder -= value;
+  }
+
+  return bits.filter(value => value).length;
+};
+
+// Log-based calculation without an array
+// TC: O(1) / SC: O(1)
+// 비트 제약이 없을 경우 -> TC: O(logn) / SC: O(1)
+var hammingWeight = function (n) {
+  const BIT_RANGE = 31;
+  let bitCount = 0;
+
+  let remainder = n;
+  while (remainder > 0) {
+    const exp = Math.min(Math.floor(Math.log2(remainder)), BIT_RANGE - 1);
+    const value = remainder <= 1 ? 1 : Math.pow(2, exp);
+    remainder -= value;
+    bitCount++;
+  }
+
+  return bitCount;
+};
+
+// Converting binary string with the JS feature
+// TC: O(1) / SC: O(1)
+// 비트 제약이 없을 경우 -> TC: O(logn) / SC: O(logn)
+var hammingWeight = function (n) {
+  const binaryString = n.toString(2);
+  return [...binaryString].filter(v => v === '1').length;
+};
+
+// Bit manipulation
+// TC: O(1) / SC: O(1)
+// 비트 제약이 없을 경우 -> TC: O(logn) / SC: O(logn)
+var hammingWeight = function (n) {
+  let count = 0;
+
+  while (n > 0) {
+    n = n & (n - 1);
+    count++;
+  }
+
+  return count;
+};