New IB Sol

Author: rahulcode22

Dynamic-Programming/LongestCommonSubsequence.py

@@ -0,0 +1,19 @@
+def lcs(s1, s2):
+    m = len(s1)
+    n = len(s2)
+
+    dp = [[None]*(n+1) for i in range(m+1)]
+
+    for i in range(m+1):
+        for j in range(n+1):
+            if i == 0 or j == 0:
+                dp[i][j] = 0
+            elif s1[i-1] == s2[j-1]:
+                dp[i][j] = dp[i-1][j-1] + 1
+            else:
+                dp[i][j] = max(dp[i-1][j],dp[i][j-1])
+
+    return dp[m][n]
+x = "AGGTAB"
+y = "GXTXAYB"
+print "Length of LCS is ", lcs(x, y)

Dynamic-Programming/Word-break.py

@@ -0,0 +1,12 @@
+def wordBreak(s,dic):
+    segmented = [True]
+    for i in range(len(s)):
+        segmented.append(False)
+        for j in range(i,-1,-1):
+            if segmented[j] and s[j:i+1] in dic:
+                segmented[i+1] = True
+                break
+    return segmented[len(s)]
+s = "myinterviewtrainer"
+dic = ["interview","my","trainer"]
+print wordBreak(s,dic)

Dynamic-Programming/longestIncreasingSubsequence.py

@@ -0,0 +1,13 @@
+#Complexity O(n*n)
+def lis(arr):
+    n = len(arr)
+
+    dp = [1]*n
+
+    for i in range(1, n):
+        for j in range(0,i):
+            if arr[i] > arr[j] and dp[i] < dp[j] + 1:
+                dp[i] = dp[j] + 1
+    return max(dp)
+arr = [10,22,9,33,21,50,41,60]
+print "Length of LIS is ", lis(arr)

Greedy/InterleavingStrings.py

@@ -0,0 +1,51 @@
+#Complexity O(M+N)
+def isInterleaved(a,b,c):
+    i, j, k = 0, 0, 0
+
+    while k !=len(c)-1:
+        if a[i] == c[k]:
+            i += 1
+        elif b[j] == c[k]:
+            j += 1
+        else:
+            return 0
+
+        k += 1
+    if a[i-1] or b[j-1]:
+        return 0
+    return 1
+
+a = "AB"
+b = "CD"
+c = "ACBG"
+if isInterleaved(a,b,c) == 1:
+    print c + "is Interleaved of "+ a + " and " + b
+else:
+    print "Not Interleaved"
+
+
+#Dynamic Approach
+def isInterleaved(a,b,c):
+    m = len(a)
+    n = len(b)
+
+    table = [[False for i in range(n+1)] for i in range(m+1)]
+
+    if m+n != len(c):
+        return False
+
+    for i in range(m+1):
+        for j in range(n+1):
+            if i == 0 and j == 0:
+                table[i][j] = True
+            elif i == 0 and (b[j-1] == c[j-1]):
+                table[i][j] = table[i][j-1]
+            elif j == 0 and a[i-1] == c[i-1]:
+                table[i][j] = table[i-1][j]
+            elif a[i-1] == c[i+j-1] and b[j-1] != c[i+j-1]:
+                table[i][j] = table[i-1][j]
+            elif a[i-1] != c[i+j-1] and b[j-1] == c[i+j-1]:
+                table[i][j] = table[i][j-1]
+            elif a[i-1] == c[i+j-1] and b[j-1] == c[i+j-1]:
+                table[i][j] = table[i-1][j] or table[i][j-1]
+    return table[m][n]

LinkedList/Reverse-LinkedList-ii.py

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+def reverseBetween(head, m, n):
+    if m == n:
+        return head
+    dummyNode = ListNode(0)
+    dummyNode.next = head
+    prev = dummyNode
+
+    for i in range(m-1):
+        prev = prev.next
+
+    rev = None
+    curr = prev.next
+
+    for i in range(n-m+1):
+        next = curr.next
+        curr.next = rev
+        rev = curr
+        curr = next
+    prev.next.next = curr
+    prev.next = reverse
+    return dummyNode.next