Summarizes technique for solving the problem.

Author: kelvinlauKL

3Sum and 4Sum/README.md

@@ -5,19 +5,22 @@
 ## 3Sum
 
 > Given an array of integers, find all subsets of the array with 3 values where the 3 values sum up to a target number. 
-
+>
 > **Note**: The solution subsets must not contain duplicate triplets.
-
+>
 > For example, given the array [-1, 0, 1, 2, -1, -4], and the target **0**:
 > The solution set is: [[-1, 0, 1], [-1, -1, 2]] // The two **-1** values in the array are considered to be distinct
 
-There are 3 key procedures in solving this algorithm:
+There are 2 key procedures in solving this algorithm. Sorting the array, and avoiding duplicates.
 
-1. Sort the array in ascending order. This allows you to make smart decisions when moving indexes around (since duplicates will be adjacent to each other).
+### Pre-sorting
 
-2. Ignoring duplicate values
+Sorting your input array allows for powerful assumptions:
 
-3. Clever adjustment of indices for each pass. 
+* duplicates are always adjacent to each other
+* moving an index to the right increases the value, while moving an index to the left decreases the value
+
+You'll make use of these two rules to create an efficient algorithm.
 
 #### Avoiding Duplicates
 
@@ -67,8 +70,6 @@ extension BidirectionalCollection where Element: Equatable {
 }
 ```
 
-### 
-
 ## 4Sum
 Given an array S of n integers, find all subsets of the array with 4 values where the 4 values sum up to a target number.