diff --git a/puzzles/interviews/training/longest_chain_equal_K.cpp b/puzzles/interviews/training/longest_chain_equal_K.cpp
new file mode 100644
index 0000000..de87c47
--- /dev/null
+++ b/puzzles/interviews/training/longest_chain_equal_K.cpp
@@ -0,0 +1,89 @@
+
+/*
+VIM: let b:lcppflags="-std=c++14 -O2 -pthread -I."
+VIM: let b:wcppflags="/O2 /EHsc /DWIN32"
+*/
+#include <iostream>
+#include <exception>
+#include <chrono>
+#include <algorithm>
+#include <vector>
+#include <unordered_map>
+
+/*
+  snap-inc-interview-questions
+
+    You are given an array of integers and a number K. You have to find the any
+    continue sub-array whose elements sum is K. Please note that, the array may
+    have positive, negative, and zeros as its element.
+
+    The desired complexity is O(N).
+
+    Example:
+        Input: [7 0 9 -10 0 789], K = 0
+        Output: Array from index 1 to Index 1.
+
+    Input: [1 2 3 5 -10] K = 0
+    Output: Array from Index 1 to Index 4.
+
+    If K = -2, Output would have been SubArray from Index 2 to Index 4.
+*/
+
+void solution( std::vector<int> v, int K )
+{
+    int f = -1;
+    int l = -2;
+
+    std::unordered_map<int, int> m;
+    int s = 0;
+    for ( int i = 0; i < v.size(); ++i ) {
+        s+= v[i];
+        auto p = m.emplace( s, i);
+        if ( !p.second ){
+            p.first->second = i;
+        }
+    }
+
+    s = 0;
+    for ( int i = 0; i < v.size(); ++i ) {
+        auto r = m.find(s+K);
+        if ( r != m.end() && l-f < r->second - i){
+            l = r->second;
+            f = i;
+        }
+        s+= v[i];
+    }
+
+    std::cout << " {";
+    for ( auto i : v ){
+        std::cout << i << ", ";
+    }
+    std::cout << "}, " << K << " -> (" << f << ", " << l << ")" << std::endl;
+}
+
+int main ( void )
+{try{
+
+    solution({7, 0, 9, -10, 0, 789}, 0);
+    solution({1, 2, 3, 5, -10}, 0);
+    solution({1, 2, 3, 5, -10}, -2);
+    solution({1, 2, 3, 5, -10}, -10);
+    solution({1, 2, 3, 5, -10}, 1);
+    solution({7, 2, 9, -10, 0, 789}, 7);
+    solution({7, 2, 9, -10, 0, 789}, 10000);
+
+    return 0;
+}
+catch ( const std::exception& e )
+{
+    std::cerr << std::endl
+            << "std::exception(\"" << e.what() << "\")." << std::endl;
+    return 2;
+}
+catch ( ... )
+{
+    std::cerr  << std::endl
+            << "unknown exception." << std::endl;
+    return 1;
+}}
+