1+ #include < cassert>
2+ #include < iostream>
3+ #include < vector>
4+
5+ /* *
6+ * @brief Calculates the maximum water that can be trapped between vertical
7+ * lines on a 2D plane.
8+ *
9+ * Given an array of non-negative integers representing vertical lines on a 2D
10+ * plane, where the width of each line is 1, the function finds two lines that,
11+ * together with the x-axis, form a container that can hold the most water.
12+ *
13+ * The problem can be efficiently solved using a two-pointer approach. We
14+ * initialize two pointers, 'left' and 'right', at the beginning and end of the
15+ * array, respectively. The width of the container is determined by the
16+ * difference between the 'right' and 'left' pointers. To maximize the water
17+ * trapped, we choose the minimum height between the lines at the 'left' and
18+ * 'right' positions. We then calculate the water trapped by multiplying the
19+ * width and height. We move the pointers towards each other, adjusting them
20+ * based on the shorter line, as moving the pointer with the smaller height has
21+ * the potential to increase the water volume.
22+ *
23+ * @param height Vector representing the heights of vertical lines.
24+ * @return int Maximum water that can be trapped.
25+ */
26+
27+ int maxArea (const std::vector<int >& height) {
28+ int maxWater =0 ;
29+ int left =0 ;
30+ int right = height.size () -1 ;
31+
32+ while (left < right) {
33+ int width = right - left;
34+ int h =std::min (height[left], height[right]);
35+ int currentWater = width * h;
36+ maxWater =std::max (maxWater, currentWater);
37+
38+ if (height[left] < height[right]) {
39+ left++;
40+ }else {
41+ right--;
42+ }
43+ }
44+
45+ return maxWater;
46+ }
47+ /* *
48+ * @brief Tests the maxArea function with various test cases.
49+ *
50+ * The function iterates through each test case, calculates the result using the
51+ * maxArea function, checks if the result matches the expected result, and
52+ * prints a success message for each test case.
53+ */
54+
55+ void testContainerWithMostWater () {
56+ // Test cases with expected maximum water values
57+ std::vector<std::pair<std::vector<int >,int >> testCases = {
58+ {{1 ,8 ,6 ,2 ,5 ,4 ,8 ,3 ,7 },49 },
59+ {{1 ,1 },1 },
60+ {{4 ,3 ,2 ,1 ,4 },16 },
61+ {{1 ,2 ,1 },2 },
62+ };
63+ for (const auto & testCase : testCases) {
64+ const std::vector<int >& input = testCase.first ;
65+ int expected = testCase.second ;
66+
67+ // Calculate the result using the maxArea function
68+ int result =maxArea (input);
69+ assert (result == expected);
70+ std::cout <<" Test passed!"
71+ }
72+ }
73+
74+ int main () {
75+ testContainerWithMostWater ();
76+ return 0 ;
77+ }