Add DSA problems

Author: SiddharthaMishra-dev

nonrepeatingchar.py

@@ -0,0 +1,12 @@
+s="siddhartha"
+temp=dict()
+for key in s:
+    if key in temp:
+        temp[key]+=1
+    else:
+        temp[key]=1
+for key in s:
+    if temp[key]==1:
+        print(key)
+        
+    

stockbuysell.py

@@ -0,0 +1,18 @@
+arr=[100 ,180, 260, 310, 40, 535, 695]
+n=len(arr)
+aux=[0]*n
+aux[n-1]=arr[n-1]
+result=[[]]
+for i in range(n-2,-1,-1):
+    aux[i]=max(aux[i+1],arr[i])
+print(aux)
+
+max=0
+for i in range(n):
+    if (aux[i]-arr[i])>max:
+        result[0]=[arr[i],aux[i]]
+        max=aux[i]-arr[i]
+    elif (aux[i]-arr[i])==max:
+        result.append([arr[i],aux[i]])
+
+print(result)