diff --git a/lab20/lab20/main.c b/lab20/lab20/main.c
index f8f766b..f1ec88a 100644
--- a/lab20/lab20/main.c
+++ b/lab20/lab20/main.c
@@ -1,6 +1,385 @@
 #include <stdio.h>
+#include <stdlib.h>
+
+typedef struct tagNODE {
+	int data;
+	struct tagNODE* next;
+} NODE;
+
+NODE* first = NULL;
+void addToHead(int value) {
+	NODE* newNode = (NODE*)malloc(sizeof(NODE));
+	if (newNode == NULL) {
+		puts("Out of memory");
+		exit(EXIT_FAILURE);
+	}
+
+	newNode->next = first;
+	newNode->data = value;
+
+	first = newNode;
+}
+
+void printNodeList() {
+	printf("first -> ");
+	NODE* ptr = first;
+	while (ptr != NULL) {
+		printf("(%d) -> ", ptr->data);
+		ptr = ptr->next;
+	}
+	printf("NULL\n");
+}
+
+int popFromHead() {
+	if (first == NULL) {
+		puts(">>> first is NULL");
+		return 0;
+	}
+	int value = first->data;
+	NODE* delNode = first;
+	first = first->next;
+	free(delNode);
+	return value;
+}
+
+int popFromIndex(int index) {
+	if (first == NULL) {
+		puts(">>> first is NULL");
+		return 0;
+	}
+
+	if (index == 0) {
+		return popFromHead();
+	}
+
+	NODE* prev_ptr = first;
+	NODE* ptr = first->next;
+	int i = 1;
+	while (ptr != NULL) {
+		if (i == index) {
+			int value = ptr->data;
+			prev_ptr->next = ptr->next;
+			free(ptr);
+
+			return value;
+		}
+		prev_ptr = ptr;
+		ptr = ptr->next;
+		i++;
+	}
+	puts(">>> index out of range");
+	return 0;
+}
+
+int count(int value) {
+	NODE* ptr = first;
+	int counter = 0;
+	while (ptr != NULL) {
+		if (ptr->data == value) {
+			counter += 1;
+		}
+		ptr = ptr->next;
+	}
+	return counter;
+}
+
+int evenCount() {
+	NODE* ptr = first;
+	int counter = 0;
+	while (ptr != NULL) {
+		if (ptr->data % 2 == 0) {
+			counter += 1;
+		}
+		ptr = ptr->next;
+	}
+	return counter;
+}
+
+void clearNodeList() {
+	NODE* delNode;
+	while (first != NULL) {
+		delNode = first;
+		first = first->next;
+		free(delNode);
+	}
+}
+
+int nodeSum() {
+	NODE* ptr = first;
+	int sum = 0;
+	while (ptr != NULL) {
+		sum += ptr->data;
+		ptr = ptr->next;
+	}
+	return sum;
+}
+
+void test() {
+	printNodeList();
+
+	addToHead(10);
+	addToHead(10);
+	addToHead(20);
+	addToHead(30);
+	addToHead(10);
+	addToHead(20);
+
+	printNodeList();
+
+	printf_s("10 count = %d\n", count(10));
+	printf_s("20 count = %d\n", count(20));
+	printf_s("30 count = %d\n", count(30));
+
+	printf_s("popped: %d\n", popFromHead());
+	printf_s("popped: %d\n", popFromHead());
+
+	printNodeList();
+
+	printf_s("10 count = %d\n", count(10));
+	printf_s("20 count = %d\n", count(20));
+	printf_s("30 count = %d\n", count(30));
+	printf("sum = %d\n", nodeSum());
+
+	clearNodeList();
+
+	printNodeList();
+	printf_s("10 count = %d\n", count(10));
+	printf_s("20 count = %d\n", count(20));
+	printf_s("30 count = %d\n", count(30));
+
+	addToHead(1);
+	addToHead(2);
+	addToHead(3);
+	addToHead(7);
+	addToHead(4);
+	addToHead(8);
+	printNodeList();
+	printf_s("even count = %d\n", evenCount());
+}
+
+void odds10X() {
+	NODE* ptr = first;
+	while (ptr != NULL) {
+		if (ptr->data % 2 != 0) {
+			ptr->data *= 10;
+		}
+		ptr = ptr->next;
+	}
+}
+
+void elementIx100(int i) {
+	NODE* ptr = first;
+	int index = 0;
+	while (ptr != NULL) {
+		if (index == i) {
+			ptr->data *= 100;
+		}
+		ptr = ptr->next;
+		index += 1;
+	}
+}
+
+void listTemplate() {
+	clearNodeList();
+	addToHead(1);
+	addToHead(2);
+	addToHead(3);
+	addToHead(7);
+	addToHead(4);
+	addToHead(8);
+}
+
+void task4() {
+	printf("\n======  task4  ======\n");
+	listTemplate();
+	printNodeList();
+	odds10X();
+	printNodeList();
+}
+
+void task5() {
+	printf("\n======  task5  ======\n");
+	listTemplate();
+	printNodeList();
+	elementIx100(1);
+	elementIx100(2);
+	elementIx100(4);
+	printNodeList();
+}
+
+void leftToIx10(int i) {
+	NODE* ptr = first;
+	int index = 0;
+	while (ptr != NULL) {
+		if (index > i) {
+			ptr->data *= 10;
+		}
+		ptr = ptr->next;
+		index += 1;
+	}
+}
+
+void task6() {
+	printf("\n======  task6  ======\n");
+	listTemplate();
+	printNodeList();
+	leftToIx10(2);
+	printNodeList();
+}
+
+void rightToIx10(int i) {
+	NODE* ptr = first;
+	int index = 0;
+	while (ptr != NULL) {
+		if (index < i) {
+			ptr->data *= 10;
+		}
+		ptr = ptr->next;
+		index += 1;
+	}
+}
+
+void task7() {
+	printf("\n======  task7  ======\n");
+	listTemplate();
+	printNodeList();
+	rightToIx10(3);
+	printNodeList();
+}
+
+void task8() {
+	printf("\n======  task8  ======\n");
+	listTemplate();
+	printNodeList();
+	printf("popped: %d\n", popFromIndex(3));
+	printNodeList();
+
+	clearNodeList();
+	addToHead(10);
+	addToHead(20);
+	addToHead(30);
+	addToHead(40);
+	addToHead(50);
+
+	printNodeList();
+	printf("popped: %d\n", popFromIndex(-1));
+	printNodeList();
+}
+
+void reversePrint(NODE* ptr) {
+	if (ptr == NULL) {
+		printf("NULL <- ");
+		return;
+	}
+	reversePrint(ptr->next);
+	printf("(%d) <- ", ptr->data);
+}
+
+void task9() {
+	printf("\n======  task9  ======\n");
+	listTemplate();
+	printNodeList();
+	
+	reversePrint(first);
+	printf("first");
+}
+
+void detectRepeats() {
+	NODE* ptr = first;
+	while (ptr != NULL) {
+		if (count(ptr->data) > 1) {
+			printf("repeats detected!\n");
+			return;
+		}
+		ptr = ptr->next;
+	}
+	printf("no repeats\n");
+}
+
+void task10() {
+	printf("\n======  task10  ======\n");
+	listTemplate();
+	printNodeList();
+	detectRepeats();
+	addToHead(1);
+	printNodeList();
+	detectRepeats();
+}
+
+void swap(int i, int j) {
+	NODE* ptr = first;
+	int i_data = 0, j_data = 0;
+	int index = 0;
+	while (ptr != NULL) {
+		if (index == i) {
+			i_data = ptr->data;
+		}
+		if (index == j) {
+			j_data = ptr->data;
+		}
+		ptr = ptr->next;
+		index++;
+	}
+	ptr = first;
+	index = 0;
+	while (ptr != NULL) {
+		if (index == i) {
+			ptr->data = j_data;
+		}
+		if (index == j) {
+			ptr->data = i_data;
+		}
+		ptr = ptr->next;
+		index++;
+	}
+}
+
+void bubbleSort() {
+	NODE* ptri = first;
+	int i = 0;
+	while (ptri->next != NULL) {
+		NODE* ptrj = first;
+		int j = 0;
+		while (ptrj->next != NULL) {
+			if (ptrj->data > ptrj->next->data) {
+				swap(j, j + 1);
+			}
+			j++;
+			ptrj = ptrj->next;
+		}
+		i++;
+		ptri = ptri->next;
+	}
+}
+
+void task12() {
+	printf("\n======  task12  ======\n");
+	listTemplate();
+	printNodeList();
+	swap(1, 4);
+	printNodeList();
+}
+
+void task13() {
+	printf("\n======  task13  ======\n");
+	listTemplate();
+	printNodeList();
+	bubbleSort();
+	printNodeList();
+}
 
 int main() {
+	test();
+
+	task4();
+	task5();
+	task6();
+	task7();
+	task8();
+	task9();
+	task10();
+	task12();
+	task13();
 
 	return 0;
 }
\ No newline at end of file
diff --git a/Лекции/FIST2024_OsnProgram_lek_11_Simvoly_Stroki.pptx b/Лекции/FIST2024_OsnProgram_lek_11_Simvoly_Stroki.pptx
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