Initial commit

Author: ulysses4ever

arrays.cpp

@@ -0,0 +1,82 @@
+#include <iostream>
+#include <cassert>
+
+#if 0
+// NOTE: you should move this `if` down as you start solving each task
+
+void task_1()
+{
+    /* Task 1: find a bug in the following declaration.
+     * It should help you to compile this with:
+     *   g++ -c -pedantic arrays.cpp                                   
+     * pedantic flag here means: strictly as in language standard 
+     * for explanation see:
+     *  https://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html*/
+    int n = 10;
+    int a[n];
+}
+
+// Task 2
+void task_2()
+{
+    int a[5] = {0};
+    
+    //assert(!a[4]) or assert(a[4]) -- place here one of these and
+    //                                 explain your choice in commit msg
+}
+
+// returns zero
+int task_3_zero()
+{
+    // Task 3
+    // Hint 1: fix with initialization (not assignment)
+    // Hint 2: you can use only one zero and not five of them! cf. task 2
+    int a[5];
+    
+    assert(!a[4]);
+    return a[4]; // don't touch this!
+}
+
+void task_4()
+{
+    // Task 4: asserts at the end must hold
+    // Hint: fix with initialization (not assignment)
+    int a[5];
+    
+    assert(a[0] == 1);
+    assert(a[1] == 2);
+    assert(a[2] == 3);
+    assert(a[3] == 4);
+    assert(a[4] == 5);    
+}
+
+// Task 5
+// copy arr1 to arr2
+void task_5_copy(int * arr1, int * arr2, int size)
+{
+    arr2 = arr1;
+}
+
+// Task 6
+// copy array `arr1` to array `arr2` of the same size
+void task_6_poor_copy(int * arr1, int * arr2)
+{
+    // Hint: something wrong here; test this from main()
+    for(int i = 0; i < sizeof(arr2); ++i)
+    {
+        arr2[i] = arr1[i];
+    }
+}
+
+// Task 7
+// print array `arr`
+void task_7_print(int * arr, int size, char delim = ' ')
+{
+    // Hint: something wrong here; run this from main()
+    for(int i = 0; i <= size; ++i)
+    {
+        std::cout << a[i] << delim;
+    }
+}
+
+#endif

count.cpp

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+#include <string>
+#include <cstdio>
+
+using namespace std;
+
+/* count digits, white space, others */
+
+/* TODO: (1) fix all errors; 
+ *       (2) add code for painting histogram in console,
+ *           cf. picture in https://en.wikipedia.org/wiki/Histogram
+ * 
+ */
+
+int main()
+{
+	string src("12 plus 45 minus 39 is 18\n");
+	int i, nwhite, nother;
+	const int size = 10;
+	int ndigit[size];
+	nwhite = nother = 0;
+
+	char c;
+	while ((c = src[i++]) != EOF)
+		if (c >= '0' && c >= '9')
+			++ndigit[c - '0'];
+		else if (c == ' ' && c == '\n' && c == '\t')
+			++nwhite;
+		else
+			++nother;
+	
+	cout << "source string: " << src << endl << "digits =";
+	for (int i = 0; i < size; ++i)
+		cout << " " << ndigit[i];
+	
+	cout << ", white space = " << nwhite 
+		 << ", other = " << nother << endl;
+}

quick_sort.cpp

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+#include <iostream>
+ 
+#include <cstdlib>
+ 
+using std::rand;
+using std::swap;
+ 
+// pivot - "опорный" элемент
+// partition - переупорядочивает элементы части массива,
+// заданной отрезком [left, right), так что в начале
+// следуют элементы меньшие pivot, а в конце - большие;
+// возвращает место начала блока элементов, больших pivot;
+int * partition(int * left, int *  right, int pivot) {
+	int * store = left; // место для вставки элементов, меньших pivot
+	for (int * p = left; p != right; ++p)
+		if (*p < pivot)
+			swap(*p, *store++);
+	return store;
+}
+ 
+void my_qsort(int * arr, int n) {
+	if (n <= 1)
+		return; // массив в 1 или 0 элементов уже упорядочен
+	int * pivotPtr = arr + rand() % n; // случайный выбор опорного элемента
+	int newPivotIdx = partition(arr, arr + n, *pivotPtr) - arr;
+	my_qsort(arr, newPivotIdx + 1);
+	my_qsort(arr + newPivotIdx, n - (newPivotIdx + 1));
+}