From 0199c8c0b5f9b1b0ea212ca008d3f3efc6a3993d Mon Sep 17 00:00:00 2001
From: aI-Iab <barry90@interia.pl>
Date: Sun, 1 May 2022 09:24:05 +0200
Subject: [PATCH] C# solution for "Subarray Sum Equals K" problem

Linear solution for https://leetcode.com/problems/subarray-sum-equals-k/
---
 cs/SubarraySumEqualsK.cs | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 cs/SubarraySumEqualsK.cs

diff --git a/cs/SubarraySumEqualsK.cs b/cs/SubarraySumEqualsK.cs
new file mode 100644
index 000000000..8c65f46e9
--- /dev/null
+++ b/cs/SubarraySumEqualsK.cs
@@ -0,0 +1,30 @@
+public class Solution {
+    public int SubarraySum(int[] nums, int k) {
+        Dictionary<int, int> prefixSums = new Dictionary<int, int>();
+        int subarrayCount = 0;
+        int currentSum = 0;
+        int diff = 0;
+        
+        for(int i = 0; i < nums.Length; i++) {
+            currentSum += nums[i];
+            
+            if(currentSum == k) {
+                subarrayCount++;
+            }
+            
+            diff = currentSum - k;
+            
+            if(prefixSums.ContainsKey(diff)) {
+                subarrayCount += prefixSums[diff];
+            }
+            
+            if(!prefixSums.ContainsKey(currentSum)) {
+                prefixSums.Add(currentSum, 0);
+            }
+            
+            prefixSums[currentSum]++;
+        }
+        
+        return subarrayCount;
+    }
+}