Solution Found using two pointers, increase left if next value larger, same with right

NeetCodeRoadmap/Two_Pointers/42_Trapping_Rain_Water.py

@@ -0,0 +1,87 @@
+# def trap(height):
+    # n = len(height)
+    # rain = 0
+    # l = 0
+    # r = n - 1
+    # l_max = height[l]
+    # r_max = height[r]
+    
+    # while l < r-1:
+    #     l += 1
+    #     if height[l] > l_max:
+    #         l_max = height[l]
+    #     else:
+    #         rain += l_max - height[l]
+    #         print(rain)
+    #         r -= 1
+    #         if height[r] > r_max:
+    #             r_max = height[r]
+    #         else:
+    #             rain += r_max - height[r]
+    #             print(rain)
+    # return rain
+def sumBackets(self, height: list[int], left, right):
+
+    minHeightLeft = height[left]
+    total = 0
+    leftBacket = 0
+    locationMinLeft = left
+
+    while left < right:
+        
+        if height[left] < minHeightLeft:
+            leftBacket += minHeightLeft - height[left]                
+        else:
+            minHeightLeft = height[left]
+            total +=  leftBacket
+            leftBacket = 0
+            locationMinLeft = left            
+        left += 1
+        
+    if minHeightLeft <= height[right]:
+        return total + leftBacket, right
+    else :      
+        return total, locationMinLeft
+
+
+def sumBacketsReverce(self, height: list[int], left, right):
+
+    minHeightRight = height[right]
+    total = 0
+    rightBacket = 0
+    locationMinRight = right
+
+    while left < right:
+        
+        if height[right] < minHeightRight:
+            rightBacket += minHeightRight - height[right]                
+        else :
+            minHeightRight = height[right]
+            total +=  rightBacket
+            rightBacket = 0
+            locationMinRight = right            
+        right -= 1
+
+    if minHeightRight <= height[left]:
+        return total + rightBacket, left
+    else :
+        return total, locationMinRight
+
+
+def trap(self, height: List[int]) -> int:                      
+    right = len(height)-1
+    left =0
+    totalSum =0
+
+
+    while left < right-1:            
+        if( height[left]< height[right]):
+            total, left = self.sumBackets(height, left, right)    
+        else:
+            total, right = self.sumBacketsReverce(height, left, right)        
+            
+        totalSum += total       
+    return totalSum
+
+# print(trap([0,1,0,2,1,0,1,3,2,1,2,1])) # Output: 6
+print(trap([4,2,0,3,2,5])) # Output: 9