Add DSA problems

longestprefix.py

@@ -0,0 +1,28 @@
+arr=['hello','world','hell']
+minword=min(arr)
+print(minword)
+prefix=""
+for i in arr:
+    temp=""
+    for j in range(len(minword)):
+        if i[j] == minword[j]:
+            temp+=minword[j]
+    if prefix=="":
+        prefix=temp        
+    if len(prefix)>len(temp):
+        prefix=temp
+
+flag=1
+for i in arr:
+    if prefix[0] != i[0]:
+        flag=0
+        break
+
+if flag==1:
+    print(prefix)
+else:
+    print("no common element")
+
+
+
+

nextgreaterelement.py

@@ -0,0 +1,16 @@
+arr=[1,3,2,4]
+n=len(arr)
+stack=[]
+result=[0]*n
+for i in range(n-1,-1,-1):
+    while stack and stack[-1]<=arr[i]:
+        stack.pop()
+    if stack:
+        result[i]=stack[-1]
+    stack.append(arr[i])
+
+for i in range(n):
+    if result[i]==0:
+        result[i]=-1
+
+print(result)

strings.py

@@ -0,0 +1,8 @@
+s1="siddhartha"
+s2='siddhantha'
+temp=[]
+for i in s1:
+    if i not in temp:
+        temp.append(i)
+
+print(temp)

trappingrainwater.py

@@ -0,0 +1,18 @@
+arr=[3,1,2,4,0,1,3,2]
+n=len(arr)
+left=[]
+right=[0]*n
+left.append(arr[0])
+for i in range(1,n):
+    left.append(max(arr[i],left[i-1]))
+
+print(left)
+right[n-1]=arr[n-1]
+for i in range(n-2,-1,-1):
+    right[i]=max(right[i+1],arr[i])
+
+
+total=0
+for i in range(0,n):
+    total=total+(min(left[i],right[i])-arr[i])
+print(total)