From c8863e33f26d4a349f90917008ddf7d6287b843a Mon Sep 17 00:00:00 2001
From: tanishk-agarwal <88491381+tanishk-agarwal@users.noreply.github.com>
Date: Thu, 21 Oct 2021 18:28:30 +0530
Subject: [PATCH] chore(C): add maximum difference in an Array (#603)

---
 algorithms/C/README.md                   | 13 +++++-
 algorithms/C/arrays/maximum-difference.c | 56 ++++++++++++++++++++++
 algorithms/C/arrays/reverse-array.c      | 59 ++++++++++++++++++++++++
 3 files changed, 127 insertions(+), 1 deletion(-)
 create mode 100644 algorithms/C/arrays/maximum-difference.c
 create mode 100644 algorithms/C/arrays/reverse-array.c

diff --git a/algorithms/C/README.md b/algorithms/C/README.md
index 140bdd49..8d19b2b5 100644
--- a/algorithms/C/README.md
+++ b/algorithms/C/README.md
@@ -1,19 +1,24 @@
 # C
 
 ## Arrays
+
 - [Even and Odd](arrays/even-and-odd.c)
 - [Unique Elements in an array](arrays/unique-elements-in-an-array.c)
+- [Reverse an array](arrays/reverse-array.c)
+- [Maximum difference](arrays/maximum-difference.c)
 
 ## Bit Manipulation
+
 - [Add and Subtract](bit-manipulation/add-and-sub-bitwise.c)
 - [Multiply](bit-manipulation/multiply-bitwise.c)
 - [Divide bitwise](bit-manipulation/divide-bitwise.c)
 
-
 ## Graphs
+
 - [Prim's Algorithm](graphs/Prim's-algorithm.c)
 
 ## Linked Lists
+
 - [Insert and Delete at Beginning](linked-lists/Insert-and-delete-beginning.c)
 - [Josephus Problem](linked-lists/josephus-problem.c)
 - [Circular Linked List](linked-lists/Insert-and-del-beginning-circular-ll.c)
@@ -23,12 +28,15 @@
 - [Glued-Linked-List](linked-lists/gl-threads.c)
 
 ## Maths
+
 - [Palindrome Number](maths/palindrome.c)
 
 ## Queues
+
 - [Double Ended Queue using array](queues/double-ended-queue-using-array.c)
 
 ## Sorting
+
 - [Bubble Sort](sorting/bubble-sort.c)
 - [Merge Sort](sorting/merge-sort.c)
 - [Insertion Sort](sorting/insertion-sort.c)
@@ -36,12 +44,14 @@
 - [Selection Sort](sorting/selection-sort.c)
 
 ## Strings
+
 - [Count Words](strings/count-words.c)
 - [Palindrome](strings/palindrome.c)
 - [Permutation of String](strings/Permutation-of-String.c)
 - [Longest Common Subsequence](strings/longest-common-subsequence.c)
 
 ## Tree
+
 - [Height Of Tree](tree/height-of-a-tree.c)
 - [Max and Min Element Of Tree](tree/min-and-max-of-tree.c)
 - [Binary Search Tree](tree/binary-search-tree.c)
@@ -50,6 +60,7 @@
 - [Max Heap](tree/max-heap.c)
 
 ## Searching
+
 - [Binary Search](searching/Binary-search.c)
 - [Jump Search](searching/Jump-search.c)
 - [Ternary Search](searching/Ternary-search.c)
diff --git a/algorithms/C/arrays/maximum-difference.c b/algorithms/C/arrays/maximum-difference.c
new file mode 100644
index 00000000..efd8b908
--- /dev/null
+++ b/algorithms/C/arrays/maximum-difference.c
@@ -0,0 +1,56 @@
+/* PROBLEM: Given an array arr[] of integers, find out the maximum difference between any two elements such that larger element appears after the smaller number.  */
+
+#include <stdio.h>
+
+/* The function assumes that there are at least two
+elements in array.
+The function returns a negative value if the array is
+sorted in decreasing order.
+Returns 0 if elements are equal */
+int maxDiff(int arr[], int arr_size)
+{
+    int max_diff = arr[1] - arr[0];
+    int min_element = arr[0];
+    int i;
+    for (i = 1; i < arr_size; i++)
+    {
+        if (arr[i] - min_element > max_diff)
+            max_diff = arr[i] - min_element;
+        if (arr[i] < min_element)
+            min_element = arr[i];
+    }
+    return max_diff;
+}
+
+int main()
+{
+    int n;
+    printf("Enter n : "); // n is number of elements in the array
+    scanf("%d", &n);
+    int arr[n];
+    if(n<2){
+        printf("Invalid Input!!!");
+        return 0;
+    }
+    for (int i = 0; i < n; i++)
+    {
+        scanf("%d", &arr[i]);
+    }
+    printf("Maximum difference is %d\n", maxDiff(arr, n));
+    getchar();
+    return 0;
+}
+
+/*
+Case 1:
+Input: Enter size: 5
+       1  2   3   4   5
+Output: Maximum difference is 4
+
+Case 2:
+Input: Enter size: 6
+        7  9  5  6  3  2
+Output: Maximum  difference is 5
+
+Time complexity: O(N) where N is the size of array
+*/
diff --git a/algorithms/C/arrays/reverse-array.c b/algorithms/C/arrays/reverse-array.c
new file mode 100644
index 00000000..438afc56
--- /dev/null
+++ b/algorithms/C/arrays/reverse-array.c
@@ -0,0 +1,59 @@
+/*PROBLEM:Given an array, of size n, reverse it. */
+
+#include <stdio.h>
+
+/* Function to reverse arr[] from start to end*/
+void rvereseArray(int arr[], int start, int end)
+{
+    int temp;
+    while (start < end)
+    {
+        temp = arr[start];
+        arr[start] = arr[end];
+        arr[end] = temp;
+        start++;
+        end--;
+    }
+}
+
+/* Function to print out an array on a line */
+void printArray(int arr[], int size)
+{
+    int i;
+    for (i = 0; i < size; i++)
+        printf("%d ", arr[i]);
+
+    printf("\n");
+}
+
+int main()
+{
+    int n;
+    printf("Enter n : "); //n is number of elements in the array
+    scanf("%d", &n);
+    int arr[n];
+    for (int i = 0; i < n; i++)
+    {
+        scanf("%d", &arr[i]);
+    }
+    rvereseArray(arr, 0, n - 1);
+    printf("Reversed array is \n");
+    printArray(arr, n);
+    return 0;
+}
+
+/*
+Case 1:
+Input: Enter size: 5
+       1  2   3   4   5
+Output: Reversed array is
+       5  4   3   2   1
+
+Case 2:
+Input: Enter size: 7
+       1  13  15  20  12  13  2 
+Output: Reversed array is
+       2  13  12  20  15  13  1 
+
+Time complexity: O(N) where N is the size of array
+*/