Problem 165: Product except self

Author: mandliya

README.md

@@ -234,5 +234,6 @@ Include contains single header implementation of data structures and some algori
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 | Write a function that takes a string as input and reverse only the vowels of a string.|[reverse_vowels.cpp](leet_code_problems/reverse_vowels.cpp)|
 | Given a string, sort it in decreasing order based on the frequency of characters.For example: <ul><li>Input: cccbbbbaa Output: bbbcccaa</li></ul>| [sortCharByFrequency.cpp](leet_code_problems/sortCharByFrequency.cpp)|
+|Product of Array Except Self. Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].| [product_except_self.cpp](leet_code_problems/product_except_self.cpp)|
 
 

leet_code_problems/product_except_self.cpp

@@ -0,0 +1,43 @@
+/*
+ * Given an array of n integers where n > 1, nums, return an array output
+ * such that output[i] is equal to the product of all the elements of nums except nums[i].
+ * Example: [1, 2, 3, 4] ==> [24, 12, 8, 6]
+ * 
+ * Try to use constant space. (excluding result array)
+ */
+
+#include <iostream>
+#include <vector>
+
+std::vector<int> product_except_self(const std::vector<int>& nums)
+{
+    int product_from_beginning = 1;
+    int product_from_end = 1;
+    unsigned int n = nums.size();
+    std::vector<int> result(n, 1);
+    for (unsigned int i = 0; i < n; ++i) {
+        result[i] *= product_from_beginning;
+        product_from_beginning *= nums[i];
+        result[n-1-i] *= product_from_end;
+        product_from_end *= nums[n-1-i];
+    }
+    return result;
+}
+void print_vector(const std::vector<int>& vec)
+{
+    for (auto n : vec) {
+        std::cout << n << " ";
+    }
+    std::cout << std::endl;
+}
+
+int main()
+{
+    std::vector<int> vec{1, 2, 3, 4};
+    std::cout << "Input Vector: ";
+    print_vector(vec);
+    std::vector<int> result = product_except_self(vec);
+    std::cout << "Output Vector: ";
+    print_vector(result);
+}
+