feat(src): add 7-reverse, 9-isPalindrome, 11-maxArea

Author: kwu130

src/11-maxArea.cpp

@@ -0,0 +1,38 @@
+//
+// Created by 1412 on 2025/10/8.
+//
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+class Solution {
+public:
+    int maxArea(vector<int>& height) {
+        int res = 0;
+        int i = 0, j = height.size() - 1;
+        while (i < j) {
+            int area = (j - i) * min(height[i], height[j]);
+            res = max(res, area);
+            if (height[i] < height[j]) {
+                i++;
+            } else {
+                j--;
+            }
+        }
+        return res;
+    }
+};
+
+void test() {
+    Solution s;
+    vector<int> height = {1, 8, 6, 2, 5, 4, 8, 3, 7};
+    assert(s.maxArea(height) == 49);
+    height = {1, 1};
+    assert(s.maxArea(height) == 1);
+}
+
+int main() {
+    test();
+    return 0;
+}

src/7-reverse.cpp

@@ -0,0 +1,36 @@
+//
+// Created by 1412 on 2025/9/29.
+//
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+class Solution {
+public:
+    int reverse(int x) {
+        int res = 0;
+        while (x) {
+            if (res < INT_MIN / 10 || res > INT_MAX / 10) {
+                return 0;
+            }
+            res = res * 10 + x % 10;
+            x /= 10;
+        }
+        return res;
+    }
+};
+
+void test() {
+    Solution s;
+    assert(s.reverse(123) == 321);
+    assert(s.reverse(-123) == -321);
+    assert(s.reverse(120) == 21);
+    assert(s.reverse(0) == 0);
+    assert(s.reverse(-2147483412) == -2143847412);
+}
+
+int main() {
+    test();
+    return 0;
+}

src/9-isPalindrome.cpp

@@ -0,0 +1,32 @@
+//
+// Created by 1412 on 2025/10/7.
+//
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+class Solution {
+public:
+    bool isPalindrome(int x) {
+        if (x < 0 || (x % 10 == 0 && x != 0)) return false;
+        int revertedNumber = 0;
+        while (x > revertedNumber) {
+            revertedNumber = revertedNumber * 10 + x % 10;
+            x /= 10;
+        }
+        return x == revertedNumber || x == revertedNumber / 10;
+    }
+};
+
+void test() {
+    Solution s;
+    assert(s.isPalindrome(121) == true);
+    assert(s.isPalindrome(-121) == false);
+    assert(s.isPalindrome(10) == false);
+}
+
+int main() {
+    test();
+    return 0;
+}