Update 112_path_sum.md

Author: Joseph Luce

leetcode/easy/112_path_sum.md

@@ -7,8 +7,7 @@
 
 Keeping track of the sum as we go down the tree is one way. 
 So that when we reach a leaf node (no children), we can check the current sum against the target sum.
-Since its recursion, the current sum before the recursion call would be used so we don't need to subtract from the current sum.
-We let recursion do that for us.
+Since its recursion, the current sum before the recursion call would be reused if we hit a dead end, so we don't need to do any subtraction from the current sum, we let recursion do that for us.
 
 Since we will be visiting all the nodes, the runtime is O(N). 
 In the worst case, we would have to have every node on the stack if the whole tree was just a linked list, space would be O(N).