feat(src): add 26-removeDuplicates, 27-removeElement, 28-strStr

Author: kwu130

src/26-removeDuplicates.cpp

@@ -0,0 +1,39 @@
+//
+// Created by 1412 on 2025/10/17.
+//
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+class Solution {
+public:
+    int removeDuplicates(vector<int>& nums) {
+        if (nums.empty()) return 0;
+        int res = 0;
+        for (int i = 1; i < nums.size(); i++) {
+            if (nums[res] != nums[i]) {
+                nums[++res] = nums[i];
+            }
+        }
+        return res + 1;
+    }
+};
+
+void test() {
+    Solution s;
+    vector<int> nums = {1, 1, 2};
+    vector<int> expected = {1, 2};
+    assert(s.removeDuplicates(nums) == expected.size());
+    assert(vector<int>(nums.begin(), nums.begin() + expected.size()) == expected);
+
+    nums = {0, 0, 1, 1, 1, 2, 2, 3, 3, 4};
+    expected = {0, 1, 2, 3, 4};
+    assert(s.removeDuplicates(nums) == expected.size());
+    assert(vector<int>(nums.begin(), nums.begin() + expected.size()) == expected);
+}
+
+int main() {
+    test();
+    return 0;
+}

src/27-removeElement.cpp

@@ -0,0 +1,44 @@
+//
+// Created by 1412 on 2025/10/17.
+//
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+class Solution {
+public:
+    int removeElement(vector<int>& nums, int val) {
+        if (nums.empty()) return 0;
+        int res = -1;
+        for (int i = 0; i < nums.size(); i++) {
+            if (nums[i] != val) {
+                nums[++res] = nums[i];
+            }
+        }
+        return res + 1;
+    }
+};
+
+void test() {
+    Solution s;
+    vector<int> nums = {3, 2, 2, 3};
+    vector<int> expected = {2, 2};
+    assert(s.removeElement(nums, 3) == expected.size());
+    assert(vector<int>(nums.begin(), nums.begin() + expected.size()) == expected);
+
+    nums = {0, 1, 2, 2, 3, 0, 4, 2};
+    expected = {0, 1, 3, 0, 4};
+    assert(s.removeElement(nums, 2) == expected.size());
+    assert(vector<int>(nums.begin(), nums.begin() + expected.size()) == expected);
+
+    nums = {};
+    expected = {};
+    assert(s.removeElement(nums, 1) == expected.size());
+    assert(vector<int>(nums.begin(), nums.begin() + expected.size()) == expected);
+}
+
+int main() {
+    test();
+    return 0;
+}

src/28-strStr.cpp

@@ -0,0 +1,29 @@
+//
+// Created by 1412 on 2025/10/17.
+//
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+class Solution {
+public:
+    int strStr(string haystack, string needle) {
+        const int n = haystack.size(), m = needle.size();
+        for (int i = 0; i < n - m + 1; i++) {
+            if (haystack.substr(i, m) == needle) return i;
+        }
+        return -1;
+    }
+};
+
+void test() {
+    Solution s;
+    assert(s.strStr("sadbutsad", "sad") == 0);
+    assert(s.strStr("leetcode", "leeto") == -1);
+}
+
+int main() {
+    test();
+    return 0;
+}