diff --git a/codes/cpp/chapter_array_and_linkedlist/list.cpp b/codes/cpp/chapter_array_and_linkedlist/list.cpp
index 44bbf88c..aadf83d4 100644
--- a/codes/cpp/chapter_array_and_linkedlist/list.cpp
+++ b/codes/cpp/chapter_array_and_linkedlist/list.cpp
@@ -48,8 +48,8 @@ int main() {
     PrintUtil::printVector(list);
 
     /* 通过索引遍历列表 */
-    int count = 0;
-    for (int i = 0; i < list.size(); i++) {
+    size_t count = 0;
+    for (size_t i = 0; i < list.size(); i++) {
         count++;
     }
 
diff --git a/codes/cpp/chapter_computational_complexity/worst_best_time_complexity.cpp b/codes/cpp/chapter_computational_complexity/worst_best_time_complexity.cpp
index c2916cb4..c3f35ada 100644
--- a/codes/cpp/chapter_computational_complexity/worst_best_time_complexity.cpp
+++ b/codes/cpp/chapter_computational_complexity/worst_best_time_complexity.cpp
@@ -22,7 +22,7 @@ vector<int> randomNumbers(int n) {
 
 /* 查找数组 nums 中数字 1 所在索引 */
 int findOne(vector<int>& nums) {
-    for (int i = 0; i < nums.size(); i++) {
+    for (size_t i = 0; i < nums.size(); i++) {
         if (nums[i] == 1)
             return i;
     }
diff --git a/codes/cpp/chapter_searching/hashing_search.cpp b/codes/cpp/chapter_searching/hashing_search.cpp
index ebc2fb01..57c9f5d1 100644
--- a/codes/cpp/chapter_searching/hashing_search.cpp
+++ b/codes/cpp/chapter_searching/hashing_search.cpp
@@ -33,7 +33,7 @@ int main() {
     vector<int> nums = { 1, 5, 3, 2, 4, 7, 5, 9, 10, 8 };
     // 初始化哈希表
     unordered_map<int, int> map;
-    for (int i = 0; i < nums.size(); i++) {
+    for (size_t i = 0; i < nums.size(); i++) {
         map[nums[i]] = i;  // key: 元素，value: 索引
     }
     int index = hashingSearch(map, target);
diff --git a/codes/cpp/chapter_searching/linear_search.cpp b/codes/cpp/chapter_searching/linear_search.cpp
index 7b509276..45a08ded 100644
--- a/codes/cpp/chapter_searching/linear_search.cpp
+++ b/codes/cpp/chapter_searching/linear_search.cpp
@@ -9,7 +9,7 @@
 /* 线性查找（数组） */
 int linearSearch(vector<int>& nums, int target) {
     // 遍历数组
-    for (int i = 0; i < nums.size(); i++) {
+    for (size_t i = 0; i < nums.size(); i++) {
         // 找到目标元素，返回其索引
         if (nums[i] == target)
             return i;
diff --git a/codes/cpp/chapter_stack_and_queue/linkedlist_queue.cpp b/codes/cpp/chapter_stack_and_queue/linkedlist_queue.cpp
index ae22740d..5694e702 100644
--- a/codes/cpp/chapter_stack_and_queue/linkedlist_queue.cpp
+++ b/codes/cpp/chapter_stack_and_queue/linkedlist_queue.cpp
@@ -68,7 +68,7 @@ public:
     vector<int> toVector() {
         ListNode* node = front;
         vector<int> res(size());
-        for (int i = 0; i < res.size(); i++) {
+        for (size_t i = 0; i < res.size(); i++) {
             res[i] = node->val;
             node = node->next;
         }