misc questions

README.md

@@ -430,6 +430,11 @@ it gets converted to i-1,j-1 or we take min or max of i,j-1 and i-1,j
 ### Pattern Matching
 - [Given a text and a pattern, find all occurences of a pattern in a given text.](/pattern-matching/question1.c)
 
+### MISC
+
+- [Test whether given two strings are isomorphic or not](/misc/question1.c)
+- [Find the length of the longest suffix which is also a prefix](/misc/question2.c)
+
 ## Some important concepts to solve algos better
 
 - For extreme values refer to limits.h constants given by C

graphs/question3.c

@@ -38,6 +38,11 @@ Now each time if we traverse the array it will take us O(v) time, rather than do
 iteration only while setting the values, we push all the nodes having value zero onto a queue. Each time
 we update values in the array we push values in the queue and will printing we pop. This way
 topological sort can be done
+
+
+METHOD2:
+While doing DFT we can push elements on stack and then pop them once DFT is done. The order in which 
+elements are popped is the topological sort
 */
 
 #include <stdio.h>
@@ -49,6 +54,8 @@ int incidents[MAX];
 int queue[MAX];
 int rear = -1, front = 0;
 
+int adjMatrix[MAX][MAX];
+
 int vertexCount = 0;
 
 int queueItemCount = 0;
@@ -108,6 +115,9 @@ void addEdge(int start, int end){
 		printf("there is no head\n");
 		newGraph->arr[start].head = temp;	
 	}
+
+	//making a matrix as well
+	adjMatrix[start][end] = 1;
 }
 
 void initArray(vertices){
@@ -139,7 +149,7 @@ void findNodeWithZeroIncidents(){
 
 }
 
-void topologicalSort(){
+void topologicalSortList(){
 
 	findNodeWithZeroIncidents();
 
@@ -160,6 +170,55 @@ void topologicalSort(){
 	}
 }
 
+void findNodeWithZeroIncidentsMatrix(int vertices){
+	int i,j;
+
+	bool noIncident = true;
+	int count = 0;
+
+	for(j=0;j<vertices;j++){
+		for(i=0;i<vertices;i++){
+
+			if(adjMatrix[i][j] != 0){
+				count++;
+				noIncident = false;
+			}
+		}
+		incidents[j] = count;
+		if(noIncident){
+			// printf("enqueueing %d\n", j);
+			enqueue(j);
+			printf("%c ", customNodes[j].label);
+		}
+		noIncident = true;
+		count = 0;
+	}
+}
+
+void topologicalSortMatrix(int vertices){
+
+	int j;
+
+	findNodeWithZeroIncidentsMatrix(vertices);
+
+	while(!isQueueEmpty()){
+		int tempVertex = dequeue();
+		// printf("dequeue %d\n", tempVertex);
+		incidents[tempVertex]=-1;
+
+		for(j=0;j<vertices;j++){
+			if(adjMatrix[tempVertex][j] == 1){
+				incidents[j]--;
+				adjMatrix[tempVertex][j] = 0;
+				if(incidents[j] == 0){
+					// printf("enqueueing %d\n", j);
+					enqueue(j);		
+				}
+			}
+		}
+	}
+}
+
 void printAdjList(struct Graph *newGraph, int vertices){
 	int i;
 
@@ -175,10 +234,23 @@ void printAdjList(struct Graph *newGraph, int vertices){
 	}
 }
 
+void initMatrix(int vertices){
+	int i,j;
+
+	for(i=0;i<vertices;i++){
+		for(j=0;j<vertices;j++){
+			adjMatrix[i][j] = 0;
+		}
+	}
+}
+
 int main(){
 	int vertices = 6;
 
 	initArray(vertices);
+
+	initMatrix(vertices);
+
 	//intializing the number of custom nodes as well the adjList basis number of vertices
 	customNodes = (struct CustomNode *)malloc(sizeof(struct CustomNode)*vertices);
 	newGraph = (struct Graph *)malloc(sizeof(struct Graph));
@@ -202,7 +274,13 @@ int main(){
 
 	printAdjList(newGraph, vertices);
 
-	topologicalSort();
+	printf("list:\n");
+	topologicalSortList();
+
+	initArray(vertices);
+	printf("\n");
+	printf("matrix:\n");
+	topologicalSortMatrix(vertices);
 
 	return 0;
 }

misc/question1.c

@@ -0,0 +1,73 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#define MAX 1000
+
+int hash1[256], hash2[256];
+
+
+int cal(char *str1, char *str2){
+
+	int j;
+
+	for(j=0;j<256;j++){
+		hash1[j] = 0;
+		hash2[j] = 0;
+	}
+
+	int len1 =strlen(str1);
+	int len2 = strlen(str2);
+
+	if(len1 != len2){
+		return 0;
+	}
+	int i;
+	for(i=0;i<len1;i++){
+
+		if(hash1[str1[i]] == 0){
+
+			hash1[str1[i]] = str2[i];	
+
+		}else{
+			if(hash1[str1[i]] != str2[i]){
+
+				return 0;
+			}
+
+		}
+
+		if(hash2[str2[i]] == 0){
+			hash2[str2[i]] = str1[i];
+		}else{
+			if(hash2[str2[i]] != str1[i]){
+				return 0;
+			}
+		}
+
+	}
+
+	return 1;
+
+}
+
+int main(){
+
+	int cases;
+	scanf("%d",&cases);
+
+	int i;
+
+	char str1[MAX], str2[MAX];
+
+	for(i=0;i<cases;i++){
+		scanf("%s",str1);
+		scanf("%s",str2);
+
+		int isIsomorphic = cal(str1, str2);
+
+		printf("%d\n",isIsomorphic);
+
+	}
+
+	return 0;
+}

nextquestions.md

@@ -103,4 +103,5 @@ TODO:
 - watch DP second last video
 - trees question20 all methods (3) to be done GFG or R
 - geeks for geeks for DP
+- Graph topological sort method2 and matrix implementation of topo