find_all_pair_equal_to_given_number and reverse_an_array

nqvinh/array/find_all_pair_equal_to_given_number/Readme.md

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+# How do you find all pairs of an integer array whose sum is equal to a given number?
+
+### Solution: Pass through array to get all pairs equal to given number.
+
+#### Implementation code:
+```
+for (int i = 0; i < arraySize; ++i)
+{
+    for(int j = i + 1; j < arraySize; j++)
+    {
+        if ((array[i] + array[j]) == givenNum)
+        {
+            printf(" %d  +  %d = %d\n", array[i], array[j], givenNum);
+        }
+    }
+}
+```

nqvinh/array/find_all_pair_equal_to_given_number/main.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <stdbool.h>
+/*
+	6. How do you find all pairs of an integer array whose sum is equal to a given number?
+*/
+
+#define ARRAYSIZE 15
+
+void printArray(unsigned int array[], unsigned int arraySize)
+{
+	for (int i = 0; i < arraySize; i++)
+		printf("%d\t", array[i]);
+
+	printf("\n");
+
+	return;
+}
+
+void initArray(unsigned int array[], unsigned int arraySize)
+{
+	int i = 0;
+
+	for (i = 0; i < arraySize; i++)
+	{
+		// random number in range 1 -> 40
+		array[i] = rand() % (40 - 1 + 1) + 1;
+	}
+
+	return;
+}
+
+void findAllPair(unsigned int array[], unsigned int arraySize, unsigned int givenNum)
+{
+    bool flag = false;
+	for (int i = 0; i < arraySize; ++i)
+	{
+        for(int j = i + 1; j < arraySize; j++)
+        {
+            if ((array[i] + array[j]) == givenNum)
+            {
+                printf(" %d  +  %d = %d\n", array[i], array[j], givenNum);
+                #ifndef FIND_FLAG
+                #define FIND_FLAG
+                    flag = true;
+                #endif
+            }
+        }
+	}
+
+    if (!flag)
+    {
+        printf("can not find any pair equal to %d", givenNum);
+    }
+    return;
+}
+
+
+int main(int argc, char const *argv[])
+{
+	unsigned int array[ARRAYSIZE];
+    unsigned int givenNumber = 0;
+	// Use current time as seed for random generator
+	srand(time(0));
+
+    givenNumber = rand() % (40 - 1 + 1) + 1;
+    printf("Number: %d \n", givenNumber);
+    initArray(array, ARRAYSIZE);
+    printArray(array, ARRAYSIZE);
+    findAllPair(array, ARRAYSIZE, givenNumber);
+
+	return 0;
+}

nqvinh/array/reverse_an_array/Readme.md

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+# How do you reverse an array?
+
+### Solution: swap the first element with the last element, swap the second element with the element next to the last element, go on until meet the midle element.
+
+#### Implementation code:
+```
+for (int i = 0; i < (arraySize / 2); i++)
+{
+    swap(&array[i], &array[arraySize -1 - i]);
+}
+```

nqvinh/array/reverse_an_array/main.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <stdbool.h>
+/*
+	6. How do you reverse an array?
+*/
+
+#define ARRAYSIZE 15
+
+void swap(unsigned int *a, unsigned int *b)
+{
+	unsigned int tmp = 0;
+
+	tmp = *a;
+	*a  = *b;
+	*b  = tmp;
+
+	return;
+}
+
+void printArray(unsigned int array[], unsigned int arraySize)
+{
+	for (int i = 0; i < arraySize; i++)
+		printf("%d\t", array[i]);
+
+	printf("\n");
+
+	return;
+}
+
+void initArray(unsigned int array[], unsigned int arraySize)
+{
+	int i = 0;
+
+	for (i = 0; i < arraySize; i++)
+	{
+		// random number in range 1 -> 40
+		array[i] = rand() % (40 - 1 + 1) + 1;
+	}
+
+	return;
+}
+
+void reverseArray(unsigned int array[], unsigned int arraySize)
+{
+	for (int i = 0; i < (arraySize / 2); i++)
+	{
+        swap(&array[i], &array[arraySize -1 - i]);
+    }
+}
+
+
+int main(int argc, char const *argv[])
+{
+	unsigned int array[ARRAYSIZE];
+	// Use current time as seed for random generator
+	srand(time(0));
+
+    initArray(array, ARRAYSIZE);
+    printArray(array, ARRAYSIZE);
+
+    reverseArray(array, ARRAYSIZE);
+    printf("Array after reversing...\n");
+    printArray(array, ARRAYSIZE);
+
+	return 0;
+}