diff --git a/c/p1.cpp b/c/p1.cpp
index f1af0d7..c8ece50 100644
--- a/c/p1.cpp
+++ b/c/p1.cpp
@@ -14,8 +14,8 @@ void checkSum(int a[], int n, int t){
         table[i][0] = true;
     }
 
-    for(int i=1;i<=n;i++){
-        for(int j=1;j<=t;j++){
+    for(int i=0;i<=n;i++){
+        for(int j=0;j<=t;j++){
             if(j < a[i-1]){
                 table[i][j] = table[i-1][j];
             }
diff --git a/c/p10.cpp b/c/p10.cpp
index 08b90e0..9ee4767 100644
--- a/c/p10.cpp
+++ b/c/p10.cpp
@@ -1,5 +1,5 @@
 //CPP program to implement circular linked list
-
+//no error
 #include<bits/stdc++.h>
 using namespace std;
 struct node{            //defining the structure of the node
diff --git a/c/p11.c b/c/p11.c
index d6ef183..b67fd08 100644
--- a/c/p11.c
+++ b/c/p11.c
@@ -13,7 +13,7 @@ int isSameTree(struct TreeNode* p, struct TreeNode* q){
         return 1;
     }
     if(p->val == q->val){
-        return isSameTree(p->left, q->left) || isSameTree(p->right, q->right);
+        return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
     }
     return 0;
 }
diff --git a/c/p12.cpp b/c/p12.cpp
index 29594f4..db9e967 100644
--- a/c/p12.cpp
+++ b/c/p12.cpp
@@ -1,6 +1,6 @@
 //program to find the longest common subsequence (LCS) in two strings
 //e.g. ABCDE and AFCZE have a common subsequence of ACE
-
+//no errors
 #include <bits/stdc++.h>
 using namespace std;
 
diff --git a/c/p13.c b/c/p13.c
index 753cad1..73cff9b 100644
--- a/c/p13.c
+++ b/c/p13.c
@@ -3,7 +3,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-int i = 0;
+//int i = 0;
 
 int main(){
     int i = i;
@@ -17,7 +17,7 @@ int main(){
         printf("%d ", a[i]);
     }
     printf("\n");
-    for(i;i<m;i++){
+    for(int i=0;i<m;i++){
         printf("%d ", b[i]);
     }
 }
diff --git a/c/p14.c b/c/p14.c
index fdd4b97..1f6ae67 100644
--- a/c/p14.c
+++ b/c/p14.c
@@ -5,7 +5,7 @@
 #include<string.h>
 
 int romanToInt(char * s){
-    int *a = (int *)malloc(strlen(s) * sizeof(int));
+    int *a = (int *)malloc((strlen(s)+1) * sizeof(int));
     for(int i=0;i<strlen(s);i++){
         switch(s[i]){
             case 'I': a[i] = 1; break;
@@ -22,7 +22,10 @@ int romanToInt(char * s){
         if(a[i] < a[i+1]){
             a[i+1] -= a[i];
         }
-        num += a[i];
+        else{
+            num += a[i];
+            
+        }
     }
     num += a[strlen(s) - 1];
     return num;
diff --git a/c/p15.cpp b/c/p15.cpp
index e1d9f33..7ad200b 100644
--- a/c/p15.cpp
+++ b/c/p15.cpp
@@ -11,11 +11,11 @@ void Upper(char *word) {
 int Check(char *S) {
     for(int k = 0, v = 0; S[k]; k++)
         switch(S[k]) {
-            case A:
-            case E:
-            case I:
-            case O:
-            case U: v++;
+            case 'A':
+            case 'E':
+            case 'I':
+            case 'O':
+            case 'U': v++;
         }
     return v;
 }
diff --git a/c/p2.cpp b/c/p2.cpp
index c1a5fa7..00b4199 100644
--- a/c/p2.cpp
+++ b/c/p2.cpp
@@ -1,6 +1,6 @@
 #include<iostream>
 using namespace std;
-
+//no error
 class A{
     int variable;
 public: 
@@ -22,7 +22,7 @@ int A::func(){
     return variable;
 }
 
-int anotherFunc(A a){
+int anotherFunc(A &a){
     a.variable += 3;
     return a.variable;
 }
diff --git a/c/p3.cpp b/c/p3.cpp
index 212f550..e99b107 100644
--- a/c/p3.cpp
+++ b/c/p3.cpp
@@ -14,7 +14,7 @@ vector<int> productExceptSelf(vector<int>& nums) {
     int r = 1;
     for(int i=nums.size()-1;i>=0;i--){
         ans[i] *= r;
-        r = nums[i];
+        r = r*nums[i];
     }
     return ans;
 }
diff --git a/c/p4.cpp b/c/p4.cpp
index 1e83511..d7ac44f 100644
--- a/c/p4.cpp
+++ b/c/p4.cpp
@@ -10,10 +10,10 @@ string caesar(string s, int k, string direction){
     string ans = "";
     for(int i=0;i<s.length();i++){
         if(direction == "encode"){
-            ans += s[i] + k;
+            ans += char(((s[i] - 'a' + k) % 26) + 'a');
         }
         else if(direction == "decode"){
-            ans += s[i] - k;
+            ans += char(((s[i] - 'a' - k + 26) % 26) + 'a');
         }
     }
     return ans;
diff --git a/c/p5.c b/c/p5.c
index 09475d3..977cf80 100644
--- a/c/p5.c
+++ b/c/p5.c
@@ -6,6 +6,6 @@ void main(){
     int a=10;
     int *ptr = &a;
 
-    *ptr++;
+    (*ptr)++;
     printf("%d", *ptr);
 }
diff --git a/c/p6.c b/c/p6.c
index 2e46837..b7d4e45 100644
--- a/c/p6.c
+++ b/c/p6.c
@@ -3,7 +3,7 @@
 #include<stdio.h>
 int *fun()
 {
-    int x = 5;
+    static int x = 5;
     return &x;
 }
 int main()
diff --git a/c/p7.cpp b/c/p7.cpp
index c5ed765..e68616d 100644
--- a/c/p7.cpp
+++ b/c/p7.cpp
@@ -5,7 +5,7 @@
 using namespace std;
 
 int func(string s){
-	int counter=-1;
+	int counter=0;
 	while(counter<s.length()) 
 		counter++;
 	return counter;
diff --git a/c/p8.c b/c/p8.c
index 5379851..943d308 100644
--- a/c/p8.c
+++ b/c/p8.c
@@ -16,6 +16,6 @@ int main()
 {
     float x[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
     size_t N = 10;
-    printf("%.3g\n", computeAverage(x, &N));
+    printf("%.3f\n", computeAverage(x, &N));
     return 0;
 }
diff --git a/c/p9.c b/c/p9.c
index 62ae10a..1d0cbaf 100644
--- a/c/p9.c
+++ b/c/p9.c
@@ -9,7 +9,7 @@
  */
 
 #include <stdio.h>
-
+#include<stdlib.h>
 int* filterMultiples(int* arr, int N, int* NOut, int num) {
     int numPrimes = 0;
     *NOut = 0;
diff --git a/py/p1.py b/py/p1.py
index b648ec0..0000282 100644
--- a/py/p1.py
+++ b/py/p1.py
@@ -7,6 +7,8 @@
 def asterisk_tree(height,level):
   if level > height:
     return
+  for i in range(1,height-level+1): #for loop for adding spaces to centre the pattern
+    print(" ",end="")
   for j in range(2*level-1):
     print("*", end="")
   print()
diff --git a/py/p10.py b/py/p10.py
index cfc822f..de034f1 100644
--- a/py/p10.py
+++ b/py/p10.py
@@ -1,6 +1,8 @@
 #Finding Average RGB values using the listmaker fuction to generate list of rgb values for a pixel
 
 def listmaker(r,g,b,list1=[]):
+    if (list1!=[]):
+        list1=[]
     list1.append(r)
     list1.append(g)
     list1.append(b)
diff --git a/py/p11.py b/py/p11.py
index 3d35661..590adda 100644
--- a/py/p11.py
+++ b/py/p11.py
@@ -1,9 +1,9 @@
 # Function to convert decimal to binary number
 
 def binaryconversion(n):
-   print(n % 2,end = '')
-   if n > 1:
-       binaryconversion(n/2)
+   	if n >=1:	
+		binaryconversion(n/2)
+	print(n % 2,end = '')
 
 number=int(input("Enter Number: "))
 binaryconversion(number)
diff --git a/py/p12.py b/py/p12.py
index c5b0f4d..37ab276 100644
--- a/py/p12.py
+++ b/py/p12.py
@@ -1,6 +1,6 @@
 # Program to multiply two matrices using nested loops
 
-A = [[1,2,3],[4,5,6],[7,8,9]]
+A = [[1,2,3],[4,5,6],[7,8,9]] #no error
 B = [[10,11,12],[13,14,15],[16,17,18]]
  
 p = len(A)
diff --git a/py/p2.py b/py/p2.py
index 237c9b9..d91163d 100644
--- a/py/p2.py
+++ b/py/p2.py
@@ -2,8 +2,10 @@
 # input- 1 -> output- [1], input- 2 -> output- [2]
 
 def add_item(item, items=[]):
-   items.append(item)
-   return items
+   if len(items)!=0:
+        items.pop(0)
+    items.append(item)  
+    return items
 
 print(add_item(1))
 print(add_item(2))
diff --git a/py/p3.py b/py/p3.py
index c83d5ad..9a6e852 100644
--- a/py/p3.py
+++ b/py/p3.py
@@ -2,12 +2,11 @@
 #eg: [2, 4, 6, 17, 10] -> [17, 10] 
 
 def delete_starting_evens(list):
-  for item in list:
-    if list[0] % 2 == 0:
-      list.pop(0)
-    else:
-      break
+  for item in range(len(list),-1,-1): # changing to range 
+    if list[item]%2==0:              # eheck element at index is even
+      list.pop(item)
   return list
 
-list = [2, 8, 10, 11]
+list = [2, 8, 10, 11
+       #changes visible
 print(delete_starting_evens(list))
diff --git a/py/p4.py b/py/p4.py
index 2ae30d4..6c379cb 100644
--- a/py/p4.py
+++ b/py/p4.py
@@ -6,10 +6,10 @@ def countSort(arr):
     ans = [0 for i in range(len(arr))]
     for i in arr:
         count[i] += 1
-    for i in range(k+1):
+    for i in range(1,k+1):
         count[i] += count[i-1]
     for i in range(len(arr)-1, -1, -1):
-        ans[count[arr[i]]] = arr[i]
+        ans[count[arr[i]]-1] = arr[i]
         count[arr[i]] -= 1
     return ans 
 
diff --git a/py/p5.py b/py/p5.py
index 01e1d53..0ad5959 100644
--- a/py/p5.py
+++ b/py/p5.py
@@ -8,10 +8,10 @@ def get_number():
             val1 = input('Enter a number: ')
             val1 = int(val1)
 
-        str_to_print = '{:.1f}'.format(val1)
+        str_to_print = '{1f}'.format(val1)
         return str_to_print
 
     except ValueError:
-        get_number()
+        return get_number()
 
 print(get_number())
diff --git a/py/p6.py b/py/p6.py
index fc571ba..0976c01 100644
--- a/py/p6.py
+++ b/py/p6.py
@@ -6,7 +6,7 @@ def addBinary(a: str, b: str) -> str:
     i = len(a) - 1
     j = len(b) - 1
 
-    while i >= 0 or j >= 0:
+    while i >= 0 or j >= 0 or carry!=0:
       if i >= 0:
         carry += int(a[i])
         i -= 1
diff --git a/py/p7.py b/py/p7.py
index ad7b53f..c773f2e 100644
--- a/py/p7.py
+++ b/py/p7.py
@@ -2,7 +2,7 @@
 #e.g. 2->4->3 + 5->6->4 = 7->0->8 (342 + 465 = 807)
 
 # Definition for singly-linked list.
-class ListNode(object):
+class ListNode(object):#no error
     def __init__(self, val=0, next=None):
         self.val = val
         self.next = next
diff --git a/py/p8.py b/py/p8.py
index 4418074..03e47c3 100644
--- a/py/p8.py
+++ b/py/p8.py
@@ -27,7 +27,11 @@ def append_item(self, data):
         self.count += 1
 
     def print_foward(self):
-        print(self.iter())
+        current=self.head
+        while current:
+            item_val=current.data
+            current=current.next
+            print(item_val)
             
     def iter(self):
         # Iterate the list
diff --git a/py/p9.py b/py/p9.py
index 4ea1c58..c831eb5 100644
--- a/py/p9.py
+++ b/py/p9.py
@@ -9,9 +9,12 @@ def ispangram(str1, alphabet=string.ascii_lowercase):
     alphaset = list(alphabet)
     
     str = list(str1.lower())
-    
-    # Check if all lowercase characters in the input string covers all characters in 'alphaset'
-    return alphaset <= str
+    for i in range (0,26):
+        if alphaset[i] not in str:
+            break
+        if i==25:
+            return True
+    return False
 
 # Print the result of checking if the string is a pangram by calling the 'ispangram' function
 print(ispangram('The quick brown fox jumps over the lazy dog'))