diff --git a/src/problems/1023.camelcase-matching.jl b/src/problems/1023.camelcase-matching.jl
index 7a428f7e0..9f6721d8a 100644
--- a/src/problems/1023.camelcase-matching.jl
+++ b/src/problems/1023.camelcase-matching.jl
@@ -74,11 +74,9 @@ function matches(query, pattern)
         end
         i += 1
     end
-    return j > length(pattern) && all(!isuppercase, query[i:end])
+    return j > length(pattern) && all(islowercase, @view(query[i:end]))
 end
 
-function camelMatch(queries, pattern)
-    return [matches(query, pattern) for query in queries]
-end
+camelMatch(queries, pattern) = matches.(queries, Ref(pattern))
 
 ## @lc code=end
diff --git a/src/unresolved/28.implement-strstr.jl b/src/problems/28.implement-strstr.jl
similarity index 65%
rename from src/unresolved/28.implement-strstr.jl
rename to src/problems/28.implement-strstr.jl
index c86c7c83f..5d30b1c39 100644
--- a/src/unresolved/28.implement-strstr.jl
+++ b/src/problems/28.implement-strstr.jl
@@ -1,8 +1,8 @@
 # ---
 # title: 28. Implement strStr()
 # id: problem28
-# author: Tian Jun
-# date: 2020-10-31
+# author: Pixia1234
+# date: 2024-07-13
 # difficulty: Easy
 # categories: Two Pointers, String
 # link: <https://leetcode.com/problems/implement-strstr/description/>
@@ -61,5 +61,24 @@
 ## @lc code=start
 using LeetCode
 
-## add your code here:
+function strStr(haystack::String, needle::String)
+    needle == "" && return 0
+    for i in 1:(length(haystack) - length(needle) + 1)
+        if @view(haystack[i:(i + length(needle) - 1)]) == needle
+            return i - 1 # Notice that Julia is 1-indexed, and here we need 0-indexed so minus 1
+        end
+    end
+    return -1
+end
+
+function strStr2(haystack::AbstractString, needle::AbstractString)
+    # border case
+    isempty(needle) && return 0
+    length(needle) > length(haystack) && return -1
+    # match needle
+    needle == @view(haystack[1:length(needle)]) && return 0
+    # recursive search
+    ind = @views strStr2(haystack[2:end], needle)
+    return ind == -1 ? -1 : ind + 1
+end
 ## @lc code=end
diff --git a/src/unresolved/29.divide-two-integers.jl b/src/problems/29.divide-two-integers.jl
similarity index 76%
rename from src/unresolved/29.divide-two-integers.jl
rename to src/problems/29.divide-two-integers.jl
index 7bdd22816..e64f3f42f 100644
--- a/src/unresolved/29.divide-two-integers.jl
+++ b/src/problems/29.divide-two-integers.jl
@@ -1,8 +1,8 @@
 # ---
 # title: 29. Divide Two Integers
 # id: problem29
-# author: Tian Jun
-# date: 2020-10-31
+# author: Pixia1234
+# date: 2024-07-17
 # difficulty: Medium
 # categories: Math, Binary Search
 # link: <https://leetcode.com/problems/divide-two-integers/description/>
@@ -69,5 +69,18 @@
 ## @lc code=start
 using LeetCode
 
-## add your code here:
+function divide(dividend::Int, divisor::Int)::Int
+    sign = (dividend < 0) ⊻ (divisor < 0)
+    dividend, divisor = abs(dividend), abs(divisor)
+    result = 0
+    while dividend >= divisor
+        shift = 0
+        while dividend >= (divisor << shift)
+            shift += 1
+        end
+        dividend -= divisor << (shift - 1)
+        result += 1 << (shift - 1)
+    end
+    return sign ? -result : result
+end
 ## @lc code=end
diff --git a/src/unresolved/38.count-and-say.jl b/src/problems/38.count-and-say.jl
similarity index 71%
rename from src/unresolved/38.count-and-say.jl
rename to src/problems/38.count-and-say.jl
index ad4aa4b73..504634a2c 100644
--- a/src/unresolved/38.count-and-say.jl
+++ b/src/problems/38.count-and-say.jl
@@ -1,8 +1,8 @@
 # ---
 # title: 38. Count and Say
 # id: problem38
-# author: Tian Jun
-# date: 2020-10-31
+# author: Pixia1234
+# date: 2024-07-17
 # difficulty: Easy
 # categories: String
 # link: <https://leetcode.com/problems/count-and-say/description/>
@@ -62,5 +62,26 @@
 ## @lc code=start
 using LeetCode
 
-## add your code here:
+function countandsay(n::Int)
+    # Base case
+    n == 1 && return "1"
+    # Get the previous term
+    previous_term = countandsay(n - 1)
+    # Generate the current term by "saying" the previous term
+    current_term = ""
+    count = 0
+    current_char = previous_term[1]
+    
+    for char in previous_term
+        if char == current_char
+            count += 1
+        else
+            current_term *= string(count) * current_char
+            current_char = char
+            count = 1
+        end
+    end
+    # Append the last group
+    current_term * string(count) * current_char
+end
 ## @lc code=end
diff --git a/src/unresolved/40.combination-sum-ii.jl b/src/problems/40.combination-sum-ii.jl
similarity index 53%
rename from src/unresolved/40.combination-sum-ii.jl
rename to src/problems/40.combination-sum-ii.jl
index 6051eb3d7..563a24267 100644
--- a/src/unresolved/40.combination-sum-ii.jl
+++ b/src/problems/40.combination-sum-ii.jl
@@ -1,8 +1,8 @@
 # ---
 # title: 40. Combination Sum II
 # id: problem40
-# author: Tian Jun
-# date: 2020-10-31
+# author: Pixia1234
+# date: 2024-07-18
 # difficulty: Medium
 # categories: Array, Backtracking
 # link: <https://leetcode.com/problems/combination-sum-ii/description/>
@@ -57,5 +57,29 @@
 ## @lc code=start
 using LeetCode
 
-## add your code here:
+function combinationSum(candidates::AbstractVector{Int}, target::Int)
+    res = Vector{Vector{Int}}()
+    return combinationSum!(sort(candidates), target, Int[], res)
+end
+
+function combinationSum!(
+    candidates::AbstractVector{Int},
+    target::Int,
+    path::AbstractVector{Int},
+    res::Vector{Vector{Int}},
+)
+    # if the target is 0, we find a solution
+    target == 0 && return push!(res, copy(path))
+    length(candidates) == 0 || target < first(candidates) && return res
+
+    # use @view to avoid copying the array
+    for (i, candidate) in enumerate(candidates)
+        i > 1 && candidate == candidates[i - 1] && continue
+        candidate > target && break
+        subcandidates = @view(candidates[1:length(candidate) .!= i]) # skip the current candidate
+        combinationSum!(subcandidates, target - candidate, push!(path, candidate), res)
+    end
+    return res
+end
+
 ## @lc code=end
diff --git a/src/unresolved/46.permutations.jl b/src/problems/46.permutations.jl
similarity index 53%
rename from src/unresolved/46.permutations.jl
rename to src/problems/46.permutations.jl
index 9c8989eab..ce01193cc 100644
--- a/src/unresolved/46.permutations.jl
+++ b/src/problems/46.permutations.jl
@@ -1,8 +1,8 @@
 # ---
 # title: 46. Permutations
 # id: problem46
-# author: Tian Jun
-# date: 2020-10-31
+# author: Pixia1234
+# date: 2024-07-19
 # difficulty: Medium
 # categories: Backtracking
 # link: <https://leetcode.com/problems/permutations/description/>
@@ -50,5 +50,26 @@
 ## @lc code=start
 using LeetCode
 
-## add your code here:
+permutation(nums::Vector{Int}) = permutation!(copy(nums))
+function permutation!(nums::Vector{Int})
+    sort!(nums)
+    res = Vector{Vector{Int}}()
+    n = length(nums)
+    sizehint!(res, factorial(n))
+    function dfs(nums::Vector{Int}, path::Vector{Int}, used::Vector{Bool}, len::Int)
+        if len == n # alternatively, len = sum(used)
+            push!(res, copy(path))
+            return nothing
+        end
+        for i in 1:n
+            used[i] && continue
+            used[i] = true
+            path[len + 1] = nums[i]
+            dfs(nums, path, used, len + 1)
+            used[i] = false
+        end
+    end
+    dfs(nums, Vector{Int}(undef, n), fill(false, n), 0)
+    return res
+end
 ## @lc code=end
diff --git a/src/unresolved/47.permutations-ii.jl b/src/problems/47.permutations-ii.jl
similarity index 53%
rename from src/unresolved/47.permutations-ii.jl
rename to src/problems/47.permutations-ii.jl
index 5a7df9f5e..c7aa5bbc2 100644
--- a/src/unresolved/47.permutations-ii.jl
+++ b/src/problems/47.permutations-ii.jl
@@ -44,5 +44,27 @@
 ## @lc code=start
 using LeetCode
 
-## add your code here:
+function permutationII(nums::Vector{Int})::Vector{Vector{Int}}
+    res = Vector{Vector{Int}}()
+    n = length(nums)
+    function dfs(nums::Vector{Int}, path::Vector{Int}, used::Vector{Bool})
+        if length(path) == n
+            push!(res, copy(path))
+            return nothing
+        end
+        @inbounds for i in 1:n
+            if used[i] || (i > 1 && nums[i] == nums[i - 1] && !used[i - 1])
+                continue
+            end
+            push!(path, nums[i])
+            used[i] = true
+            dfs(nums, path, used)
+            pop!(path)
+            used[i] = false
+        end
+    end
+    sort!(nums)
+    dfs(nums, Vector{Int}(), fill(false, n))
+    return res
+end
 ## @lc code=end
diff --git a/test/problems/1023.camelcase-matching.jl b/test/problems/1023.camelcase-matching.jl
index 2a5fe37b5..04c59f063 100644
--- a/test/problems/1023.camelcase-matching.jl
+++ b/test/problems/1023.camelcase-matching.jl
@@ -1,5 +1,5 @@
 @testset "1023.camelcase-matching.jl" begin
-    @test camelMatch(("FooBar","FooBarTest","FootBall","FrameBuffer","ForceFeedBack"),"FB") == ("1,0,1,1,0")
-    @test camelMatch(("FooBar","FooBarTest","FootBall","FrameBuffer","ForceFeedBack"),"FoBa") == ("1,0,1,0,0")
-    @test camelMatch(("FooBar","FooBarTest","FootBall","FrameBuffer","ForceFeedBack"),"FoBaT") == ("0,1,0,0,0")
+    @test camelMatch(["FooBar","FooBarTest","FootBall","FrameBuffer","ForceFeedBack"],"FB") == [true,false,true,true,false]
+    @test camelMatch(["FooBar","FooBarTest","FootBall","FrameBuffer","ForceFeedBack"],"FoBa") == [true,false,true,false,false]
+    @test camelMatch(["FooBar","FooBarTest","FootBall","FrameBuffer","ForceFeedBack"],"FoBaT") == [false,true,false,false,false]
 end
diff --git a/test/problems/28.implement-strstr.jl b/test/problems/28.implement-strstr.jl
new file mode 100644
index 000000000..407b0df69
--- /dev/null
+++ b/test/problems/28.implement-strstr.jl
@@ -0,0 +1,10 @@
+@testset "28.implement-strstr.jl" begin
+    @test strStr("hello", "ll") == 2
+    @test strStr("aaaaa", "bba") == -1
+    @test strStr("sadbutsad", "sad") == 0
+    @test strStr("leetcode", "leeto") == -1
+    @test strStr2("hello", "ll") == 2
+    @test strStr2("aaaaa", "bba") == -1
+    @test strStr2("sadbutsad", "sad") == 0
+    @test strStr2("leetcode", "leeto") == -1
+end
diff --git a/test/problems/29.divide-two-integers.jl b/test/problems/29.divide-two-integers.jl
new file mode 100644
index 000000000..77c434765
--- /dev/null
+++ b/test/problems/29.divide-two-integers.jl
@@ -0,0 +1,6 @@
+@testset "29.divide-two-integers.jl" begin
+    @test divide(10, 3) == 3
+    @test divide(7, -3) == -2
+    @test divide(0, 1) == 0
+    @test divide(1, 1) == 1
+end
diff --git a/test/problems/38.count-and-say.jl b/test/problems/38.count-and-say.jl
new file mode 100644
index 000000000..78b7de06e
--- /dev/null
+++ b/test/problems/38.count-and-say.jl
@@ -0,0 +1,6 @@
+@testset "38.count-and-say.jl" begin
+    @test countandsay(1) == "1"
+    @test countandsay(4) == "1211"
+    @test countandsay(5) == "111221"
+    @test countandsay(6) == "312211"
+end
diff --git a/test/problems/40.combination-sum-ii.jl b/test/problems/40.combination-sum-ii.jl
new file mode 100644
index 000000000..dfc5f928e
--- /dev/null
+++ b/test/problems/40.combination-sum-ii.jl
@@ -0,0 +1,5 @@
+@testset "40.combination-sum-ii.jl" begin
+    @test combinationSum([10, 1, 2, 7, 6, 1, 5], 8) ==
+        [[1, 1, 6], [1, 2, 5], [1, 7], [2, 6]]
+    @test combinationSum([2, 5, 2, 1, 2], 5) == [[1, 2, 2], [5]]
+end
diff --git a/test/problems/46.permutations.jl b/test/problems/46.permutations.jl
new file mode 100644
index 000000000..f9ce03c17
--- /dev/null
+++ b/test/problems/46.permutations.jl
@@ -0,0 +1,6 @@
+@testset "46.permutations.jl" begin
+    @test sort!(permutation([1, 3, 2])) ==
+        [[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]
+    @test permutation([0, 1]) == [[0, 1], [1, 0]]
+    @test permutation([1]) == [[1]]
+end
diff --git a/test/problems/47.permutations-ii.jl b/test/problems/47.permutations-ii.jl
new file mode 100644
index 000000000..a1541455e
--- /dev/null
+++ b/test/problems/47.permutations-ii.jl
@@ -0,0 +1,5 @@
+@testset "47.permutations-ii.jl" begin
+    @test permutationII([1, 1, 2]) == [[1, 1, 2], [1, 2, 1], [2, 1, 1]]
+    @test permutationII([1, 2, 3]) ==
+        [[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]
+end