From 3c6356a97701c231eec693918a59ee3c554aae41 Mon Sep 17 00:00:00 2001
From: Saurav Gore <sauravgore97@gmail.com>
Date: Tue, 14 Jun 2022 20:19:33 +0530
Subject: [PATCH] Added Zero Sum Subarrays.cpp

---
 HashMaps/Zero Sum Subarrays.cpp | 85 +++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)
 create mode 100644 HashMaps/Zero Sum Subarrays.cpp

diff --git a/HashMaps/Zero Sum Subarrays.cpp b/HashMaps/Zero Sum Subarrays.cpp
new file mode 100644
index 0000000..ece41e9
--- /dev/null
+++ b/HashMaps/Zero Sum Subarrays.cpp	
@@ -0,0 +1,85 @@
+/*
+
+Print all subarrays with 0 sum
+
+Given an array, print all subarrays in the array which has sum 0.
+
+Examples:  
+
+Input:  arr = [6, 3, -1, -3, 4, -2, 2, 4, 6, -12, -7]
+
+Output:  
+
+Subarray found from Index 2 to 4
+Subarray found from Index 2 to 6          
+Subarray found from Index 5 to 6
+Subarray found from Index 6 to 9
+Subarray found from Index 0 to 10
+
+*/
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+// Time Complexity --> O(n^2), Space Complexity --> O(1)
+
+void zeroSubASum1(vector<int> &A, int n)
+{
+    for (int i = 0; i < n; i++)
+    {
+        if (A[i] == 0)
+            cout << "Subarray found from index " << i << " to " << i << endl;
+    }
+    for (int i = 2; i <= n; i++)
+    {
+        long long sm = 0;
+        for (int m = 0; m < i; m++)
+            sm += A[m];
+        if (sm == 0)
+            cout << "Subarray found from index " << 0 << " to " << i - 1 << endl;
+        int j = i;
+        while (j < n)
+        {
+            sm -= A[j - i];
+            sm += A[j];
+            if (sm == 0)
+                cout << "Subarray found from index " << j - i + 1 << " to " << j << endl;
+            j++;
+        }
+    }
+}
+
+// Time Complexity --> O(n), Space Complexity --> O(n)
+
+void zeroSubASum2(vector<int> &A, int n)
+{
+    unordered_map<int, vector<int>> ump;
+    long long sm = 0;
+    for (int i = 0; i < n; i++)
+    {
+        sm += A[i];
+        if (sm == 0)
+            cout << "Subarray found from index " << 0 << " to " << i << endl;
+        if (ump.find(sm) != ump.end())
+        {
+            vector<int> tmp = ump[sm];
+            for (auto x : tmp)
+                cout << "Subarray found from index " << x + 1 << " to " << i << endl;
+        }
+        ump[sm].push_back(i);
+    }
+}
+
+int main()
+{
+    int n;
+    cin >> n;
+    vector<int> A(n);
+    for (int i = 0; i < n; i++)
+        cin >> A[i];
+    zeroSubASum1(A, n);
+    cout << endl;
+    zeroSubASum2(A, n);
+    return 0;
+}