Add comments for "Container With Most Water"

src/containerWithMostWater/containerWithMostWater.cpp

@@ -17,16 +17,23 @@
 class Solution {
 public:
     int maxArea(vector<int> &height) {
-        int area = 0;
-        int i = 0; 
-        int j = height.size()-1;
 
-        while(i<j){
-            int a = (j-i)* (height[i]>height[j] ? height[j] : height[i]);
-            area = a>area ? a : area;
-            height[i]>height[j] ? j-- : i++;
+        int maxArea = 0;
+        // two pointers scan from two sides to middle
+        int left = 0; 
+        int right = height.size()-1;
+
+        int area; 
+        while ( left < right ){
+            //calculate the area
+            area = (right - left) * ( height[left] < height[right] ? height[left] : height[right]);
+            //tracking the maxium area
+            maxArea = area > maxArea ? area : maxArea;
+            // because the area is decided by the shorter edge
+            // so we increase the area is to increase the shorter edge
+            height[left] < height[right] ? left++ : right-- ;
         }
         
-        return area;
+        return maxArea;
     }
 };