feat: add reverse array function (#54)

* [add] reverse array function

Signed-off-by: Sumit Banik <[email protected]>

* [update] comparison for two uint arrays

* [add] endline in the file

* chore: removed duplicated entry

Signed-off-by: Sumit Banik <[email protected]>
Co-authored-by: David Leal <[email protected]>

Author: 0xSumitBanik

src/Maths/ReverseArray.sol

@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+/**
+ * @title Array Reversal.
+ * @author Sumit Banik https://github.com/iSumitBanik
+ * @dev Contract to demonstrate how an array is reversed.
+ */
+
+contract ReverseArray {
+        /**
+        * @dev internal function which takes in an array of numbers,start and end index,as an ouput returns the reversed array.
+        * @param _array => array of numbers
+        * @param start => start index of the array
+        * @param end => ending index of the array
+        * @return _array => reversed array.
+        */
+        function _reverseArray(
+        uint256[] memory _array,
+        uint256 start,
+        uint256 end
+    ) internal pure returns (uint256[] memory) {
+        while (start < end) {
+            (_array[start], _array[end]) = (_array[end], _array[start]);
+            start++;
+            end--;
+        }
+
+        return _array;
+    }
+    /** 
+    * @dev external function which takes in an array of numbers and as an ouput returns the reversed array.
+    * @param _array => array of numbers
+    * @return _array => reversed array using the _reverseArray internal function.
+    */
+    function reverse(uint256[] memory _array)
+        external
+        pure
+        returns (uint256[] memory)
+    {
+        uint256 end = (_array.length) - 1;
+        return _reverseArray(_array, 0, end);
+    }
+}

src/Maths/test/ReverseArray.t.sol

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+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.0;
+
+import "forge-std/Test.sol";
+import "../ReverseArray.sol";
+
+contract ReverseArrayTest is Test {
+    // Target contract
+    ReverseArray reverseArray;
+
+    /// Test Params
+    uint256[] private testArray = [202,27,123,1,66,76,2,55,111,455];
+    uint256[] private expectedreversedArray = [455, 111, 55, 2, 76, 66, 1, 123, 27, 202];
+
+    function setUp() public {
+        reverseArray = new ReverseArray();
+    }
+
+    /// @dev Test `reverseArray`
+
+    function test_reverseArray() public {
+
+        uint[] memory reversedArray = reverseArray.reverse(testArray);
+        assertEq(reversedArray,expectedreversedArray);
+    }
+}