diff --git a/doitchuu/BackspaceStringCompare.js b/doitchuu/BackspaceStringCompare.js
new file mode 100644
index 0000000..ba47a24
--- /dev/null
+++ b/doitchuu/BackspaceStringCompare.js
@@ -0,0 +1,22 @@
+/**
+ * @param {string} s
+ * @param {string} t
+ * @return {boolean}
+ */
+var backspaceCompare = function(s, t) {
+    return getRemainString(s) === getRemainString(t);
+};
+
+function getRemainString(str) {
+    const stack = [];
+
+    for (let i = 0; i < str.length; i++) {
+        if (str[i] === "#") {
+            stack.pop();
+        } else {
+            stack.push(str[i]);
+        }
+    }
+
+    return stack.join("");
+}
diff --git a/doitchuu/CountingBits.js b/doitchuu/CountingBits.js
new file mode 100644
index 0000000..7fd6778
--- /dev/null
+++ b/doitchuu/CountingBits.js
@@ -0,0 +1,18 @@
+/**
+ * @param {number} n
+ * @return {number[]}
+ */
+var countBits = function(n) {
+    const dp = [0];
+
+    if (n === 0) {
+        return dp;
+    }
+
+    for (let i = 1; i <= n; i++) {
+        const count = i.toString(2).replaceAll("0", "").length;
+        dp.push(count);
+    }
+
+    return dp;
+};
diff --git a/doitchuu/NumberOf1Bits.js b/doitchuu/NumberOf1Bits.js
new file mode 100644
index 0000000..66c9a45
--- /dev/null
+++ b/doitchuu/NumberOf1Bits.js
@@ -0,0 +1,15 @@
+/**
+ * @param {number} n - a positive integer
+ * @return {number}
+ */
+var hammingWeight = function(n) {
+    let current = n >>> 0;
+    let count = 0;
+
+    while (current !== 0) {
+        current &= current - 1;
+        count++;
+    }
+
+    return count;
+};
diff --git a/doitchuu/SameTree.js b/doitchuu/SameTree.js
new file mode 100644
index 0000000..e0a108b
--- /dev/null
+++ b/doitchuu/SameTree.js
@@ -0,0 +1,28 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} p
+ * @param {TreeNode} q
+ * @return {boolean}
+ */
+var isSameTree = function(p, q) {
+    if (p === null && q === null) {
+        return true;
+    }
+
+    if (p === null || q === null) {
+        return false;
+    }
+
+    if (p.val !== q.val) {
+        return false;
+    }
+
+    return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
+};