diff --git a/Lab_20/Lab_20.sln b/Lab_20/Lab_20.sln
new file mode 100644
index 0000000..520a9fb
--- /dev/null
+++ b/Lab_20/Lab_20.sln
@@ -0,0 +1,31 @@
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+EndProject
+Global
+ GlobalSection(SolutionConfigurationPlatforms) = preSolution
+ Debug|x64 = Debug|x64
+ Debug|x86 = Debug|x86
+ Release|x64 = Release|x64
+ Release|x86 = Release|x86
+ EndGlobalSection
+ GlobalSection(ProjectConfigurationPlatforms) = postSolution
+ {8BE85FFB-DD91-4119-BB66-A3D2B505E650}.Debug|x64.ActiveCfg = Debug|x64
+ {8BE85FFB-DD91-4119-BB66-A3D2B505E650}.Debug|x64.Build.0 = Debug|x64
+ {8BE85FFB-DD91-4119-BB66-A3D2B505E650}.Debug|x86.ActiveCfg = Debug|Win32
+ {8BE85FFB-DD91-4119-BB66-A3D2B505E650}.Debug|x86.Build.0 = Debug|Win32
+ {8BE85FFB-DD91-4119-BB66-A3D2B505E650}.Release|x64.ActiveCfg = Release|x64
+ {8BE85FFB-DD91-4119-BB66-A3D2B505E650}.Release|x64.Build.0 = Release|x64
+ {8BE85FFB-DD91-4119-BB66-A3D2B505E650}.Release|x86.ActiveCfg = Release|Win32
+ {8BE85FFB-DD91-4119-BB66-A3D2B505E650}.Release|x86.Build.0 = Release|Win32
+ EndGlobalSection
+ GlobalSection(SolutionProperties) = preSolution
+ HideSolutionNode = FALSE
+ EndGlobalSection
+ GlobalSection(ExtensibilityGlobals) = postSolution
+ SolutionGuid = {BD29D65A-3B89-43F1-A036-5AEDE6CC37A0}
+ EndGlobalSection
+EndGlobal
diff --git a/Lab_20/Lab_20/Lab_20.vcxproj b/Lab_20/Lab_20/Lab_20.vcxproj
new file mode 100644
index 0000000..1fa6b59
--- /dev/null
+++ b/Lab_20/Lab_20/Lab_20.vcxproj
@@ -0,0 +1,140 @@
+
+
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+ Win32
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+ x64
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+ Win32Proj
+ {8be85ffb-dd91-4119-bb66-a3d2b505e650}
+ Lab20
+ 10.0
+
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+ true
+ v143
+ Unicode
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+ false
+ v143
+ true
+ Unicode
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+ true
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+ Unicode
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+ v143
+ true
+ Unicode
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+ true
+ WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)
+ true
+
+
+ Console
+ true
+
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+ Level3
+ true
+ true
+ true
+ WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)
+ true
+
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+ Console
+ true
+ true
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+ true
+ _DEBUG;_CONSOLE;%(PreprocessorDefinitions)
+ true
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+ true
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diff --git a/Lab_20/Lab_20/Lab_20.vcxproj.filters b/Lab_20/Lab_20/Lab_20.vcxproj.filters
new file mode 100644
index 0000000..2ed787a
--- /dev/null
+++ b/Lab_20/Lab_20/Lab_20.vcxproj.filters
@@ -0,0 +1,37 @@
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+
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+ {4FC737F1-C7A5-4376-A066-2A32D752A2FF}
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+
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+ {93995380-89BD-4b04-88EB-625FBE52EBFB}
+ h;hh;hpp;hxx;h++;hm;inl;inc;ipp;xsd
+
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+ {67DA6AB6-F800-4c08-8B7A-83BB121AAD01}
+ rc;ico;cur;bmp;dlg;rc2;rct;bin;rgs;gif;jpg;jpeg;jpe;resx;tiff;tif;png;wav;mfcribbon-ms
+
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diff --git a/Lab_20/Lab_20/Z_1.cpp b/Lab_20/Lab_20/Z_1.cpp
new file mode 100644
index 0000000..7745dd6
--- /dev/null
+++ b/Lab_20/Lab_20/Z_1.cpp
@@ -0,0 +1,82 @@
+//#define _CRT_SECURE_NO_WARNINGS
+//
+//#include
+//#include
+//
+//struct Node {
+// int data;
+// struct Node* next;
+//};
+//
+//
+//struct Node* first = NULL;
+//
+//void printList() {
+// struct Node* ptr = first;
+// while (ptr != NULL) {
+// printf("(%d) -> ", ptr->data);
+// ptr = ptr->next;
+// }
+// printf("NULL\n");
+//}
+//
+//void addToHead(int value) {
+// struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
+//
+// newNode->next = first;
+// newNode->data = value;
+//
+// first = newNode;
+//}
+//
+//int deleteFromHead() {
+// int value = first->data;
+// struct Node* delNode = first;
+// first = first->next;
+// free(delNode);
+// return value;
+//}
+//
+//int contains(int value) {
+// struct Node* ptr = first;
+// while (ptr != NULL) {
+// if (ptr->data == value) {
+// return 1;
+// }
+// ptr = ptr->next;
+// }
+// return 0;
+//}
+//
+//void clearList() {
+// while (first != NULL)
+// {
+// struct Node* delNode = first;
+// first = first->next;
+// free(delNode);
+// }
+//}
+//
+//
+//void main() {
+// first = NULL;
+// printList();
+//
+// addToHead(400);
+// addToHead(300);
+// addToHead(200);
+// addToHead(100);
+// deleteFromHead();
+// printList();
+//
+// printf("contains(100) = %d\n", contains(100));
+// printf("contains(150) = %d\n", contains(150));
+// printf("contains(200) = %d\n", contains(200));
+//
+// clearList();
+// printList();
+//
+// printf("contains(100)(NULL) = %d\n", contains(100));
+// printf("contains(150)(NULL) = %d\n", contains(150));
+// printf("contains(200)(NULL) = %d\n", contains(200));
+//}
diff --git a/Lab_20/Lab_20/Z_2.cpp b/Lab_20/Lab_20/Z_2.cpp
new file mode 100644
index 0000000..497f52f
--- /dev/null
+++ b/Lab_20/Lab_20/Z_2.cpp
@@ -0,0 +1,69 @@
+//#define _crt_secure_no_warnings
+//
+//#include
+//#include
+//
+//struct node {
+// int data;
+// struct node* next;
+//};
+//
+//
+//struct node* first = NULL;
+//
+//void printlist() {
+// struct node* ptr = first;
+// while (ptr != NULL) {
+// printf("(%d) -> ", ptr->data);
+// ptr = ptr->next;
+// }
+// printf("null\n");
+//}
+//
+//void addtohead(int value) {
+// struct node* newnode = (struct node*)malloc(sizeof(struct node));
+//
+// newnode->next = first;
+// newnode->data = value;
+//
+// first = newnode;
+//}
+//
+//int sum() {
+// int s = 0;
+// struct node* ptr = first;
+// while (ptr != NULL) {
+// s += ptr->data;
+// ptr = ptr->next;
+// }
+// return s;
+//}
+//
+//void clearlist() {
+// while (first != NULL)
+// {
+// struct node* delnode = first;
+// first = first->next;
+// free(delnode);
+// }
+//}
+//
+//
+//void main() {
+// first = NULL;
+// printlist();
+//
+// addtohead(1);
+// addtohead(3);
+// addtohead(6);
+// addtohead(9);
+// printlist();
+//
+// printf("sum = %d\n", sum());
+//
+// clearlist();
+// printlist();
+//
+// printf("sum(null) = %d\n", sum());
+//
+//}
diff --git a/Lab_20/Lab_20/Z_3.cpp b/Lab_20/Lab_20/Z_3.cpp
new file mode 100644
index 0000000..7d17d93
--- /dev/null
+++ b/Lab_20/Lab_20/Z_3.cpp
@@ -0,0 +1,72 @@
+//#define _CRT_SECURE_NO_WARNINGS
+//
+//#include
+//#include
+//
+//struct Node {
+// int data;
+// struct Node* next;
+//};
+//
+//
+//struct Node* first = NULL;
+//
+//void printList() {
+// struct Node* ptr = first;
+// while (ptr != NULL) {
+// printf("(%d) -> ", ptr->data);
+// ptr = ptr->next;
+// }
+// printf("NULL\n");
+//}
+//
+//void addToHead(int value) {
+// struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
+//
+// newNode->next = first;
+// newNode->data = value;
+//
+// first = newNode;
+//}
+//
+//int evcnt() {
+// struct Node* ptr = first;
+// int count = 0;
+// while (ptr != NULL) {
+// if (ptr->data % 2 == 0) {
+// count++;
+//
+// }
+// ptr = ptr->next;
+// }
+// return count;
+//}
+//
+//void clearList() {
+// while (first != NULL)
+// {
+// struct Node* delNode = first;
+// first = first->next;
+// free(delNode);
+// }
+//}
+//
+//
+//void main() {
+// first = NULL;
+// printList();
+//
+// addToHead(2);
+// addToHead(3);
+// addToHead(6);
+// addToHead(4);
+// printList();
+//
+// printf("Even Num = %d\n", evcnt());
+//
+// clearList();
+// printList();
+//
+// printf("Even Num(Null) = %d\n", evcnt());
+//
+//}
diff --git a/Lab_20/Lab_20/Z_4.cpp b/Lab_20/Lab_20/Z_4.cpp
new file mode 100644
index 0000000..826d39d
--- /dev/null
+++ b/Lab_20/Lab_20/Z_4.cpp
@@ -0,0 +1,69 @@
+//#define _CRT_SECURE_NO_WARNINGS
+//
+//#include
+//#include
+//
+//struct Node {
+// int data;
+// struct Node* next;
+//};
+//
+//
+//struct Node* first = NULL;
+//
+//void printList() {
+// struct Node* ptr = first;
+// while (ptr != NULL) {
+// printf("(%d) -> ", ptr->data);
+// ptr = ptr->next;
+// }
+// printf("NULL\n");
+//}
+//
+//void addToHead(int value) {
+// struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
+//
+// newNode->next = first;
+// newNode->data = value;
+//
+// first = newNode;
+//}
+//
+//void oddsX10() {
+// struct Node* ptr = first;
+// while (ptr != NULL) {
+// if (ptr->data % 2 != 0) {
+// ptr->data *= 2;
+// }
+// ptr = ptr->next;
+// }
+//}
+//
+//void clearList() {
+// while (first != NULL)
+// {
+// struct Node* delNode = first;
+// first = first->next;
+// free(delNode);
+// }
+//}
+//
+//
+//void main() {
+// first = NULL;
+// printList();
+//
+// addToHead(2);
+// addToHead(3);
+// addToHead(6);
+// addToHead(9);
+// printList();
+//
+// oddsX10();
+// printList();
+//
+// clearList();
+// printList();
+//
+//
+//}
diff --git a/Lab_20/Lab_20/Z_5.cpp b/Lab_20/Lab_20/Z_5.cpp
new file mode 100644
index 0000000..276915a
--- /dev/null
+++ b/Lab_20/Lab_20/Z_5.cpp
@@ -0,0 +1,79 @@
+//#define _CRT_SECURE_NO_WARNINGS
+//
+//#include
+//#include
+//
+//struct Node {
+// int data;
+// struct Node* next;
+//};
+//
+//
+//struct Node* first = NULL;
+//
+//void printList() {
+// struct Node* ptr = first;
+// while (ptr != NULL) {
+// printf("(%d) -> ", ptr->data);
+// ptr = ptr->next;
+// }
+// printf("NULL\n");
+//}
+//
+//void addToHead(int value) {
+// struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
+//
+// newNode->next = first;
+// newNode->data = value;
+//
+// first = newNode;
+//}
+//
+//void elIx100(int value) {
+// struct Node* ptr = first;
+// int i = 0;
+// while (ptr != NULL) {
+// if (i == value) {
+// ptr->data *= 100;
+// }
+// ptr = ptr->next;
+// i++;
+// }
+//}
+//
+//void clearList() {
+// while (first != NULL)
+// {
+// struct Node* delNode = first;
+// first = first->next;
+// free(delNode);
+// }
+//}
+//
+//
+//void main() {
+// first = NULL;
+// printList();
+//
+// addToHead(1);
+// addToHead(3);
+// addToHead(6);
+// addToHead(8);
+// printList();
+//
+// printf("-------------------------------------------\n");
+//
+// elIx100(0);
+// printList();
+//
+// elIx100(2);
+// printList();
+//
+// elIx100(0);
+// printList();
+//
+// clearList();
+// printList();
+//
+//
+//}
diff --git a/Lab_20/Lab_20/Z_6.cpp b/Lab_20/Lab_20/Z_6.cpp
new file mode 100644
index 0000000..27dbecc
--- /dev/null
+++ b/Lab_20/Lab_20/Z_6.cpp
@@ -0,0 +1,79 @@
+#define _CRT_SECURE_NO_WARNINGS
+
+#include
+#include
+
+struct Node {
+ int data;
+ struct Node* next;
+};
+
+
+struct Node* first = NULL;
+
+void printList() {
+ struct Node* ptr = first;
+ while (ptr != NULL) {
+ printf("(%d) -> ", ptr->data);
+ ptr = ptr->next;
+ }
+ printf("NULL\n");
+}
+
+void addToHead(int value) {
+ struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
+
+ newNode->next = first;
+ newNode->data = value;
+
+ first = newNode;
+}
+
+void elLeftIx10(int value) {
+ struct Node* ptr = first;
+ int i = 0;
+ while (ptr != NULL) {
+ if (i < value) {
+ ptr->data *= 10;
+ }
+ ptr = ptr->next;
+ i++;
+ }
+}
+
+void clearList() {
+ while (first != NULL)
+ {
+ struct Node* delNode = first;
+ first = first->next;
+ free(delNode);
+ }
+}
+
+
+void main() {
+ first = NULL;
+ printList();
+
+ addToHead(1);
+ addToHead(3);
+ addToHead(6);
+ addToHead(8);
+ printList();
+
+ printf("-------------------------------------------\n");
+
+ elLeftIx10(1);
+ printList();
+
+ elLeftIx10(2);
+ printList();
+
+ elLeftIx10(4);
+ printList();
+
+ clearList();
+ printList();
+
+
+}