Can 3rd String be formed by interleaving first and second

Author: ratulb

codes/interleave_string.mojo

@@ -0,0 +1,42 @@
+### Interleaving String
+### Determine if s3 is an interleaving of s1 and s2.
+
+
+fn is_interleave(s1: String, s2: String, s3: String) -> Bool:
+    if len(s1) + len(s2) != len(s3):
+        return False
+    dp = List[List[Bool]](
+        length=len(s1) + 1, fill=List[Bool](length=len(s2) + 1, fill=False)
+    )
+    dp[len(s1)][len(s2)] = True
+    for i in range(len(s1), -1, -1):
+        for j in range(len(s2), -1, -1):
+            if i < len(s1) and s1[i] == s3[i + j] and dp[i + 1][j]:
+                dp[i][j] = True
+            if j < len(s2) and s2[j] == s3[i + j] and dp[i][j + 1]:
+                dp[i][j] = True
+
+    return dp[0][0]
+
+
+from testing import assert_true, assert_false
+
+
+fn main() raises:
+    var s1: String = "aabcc"
+    var s2: String = "dbbca"
+    var s3: String = "aadbbcbcac"
+    result = is_interleave(s1, s2, s3)
+    assert_true(result, "Assertion failed")
+
+    s1 = "aabcc"
+    s2 = "dbbca"
+    s3 = "aadbbbaccc"
+    result = is_interleave(s1, s2, s3)
+    assert_false(result, "Assertion failed")
+
+    s1 = ""
+    s2 = ""
+    s3 = ""
+    result = is_interleave(s1, s2, s3)
+    assert_true(result, "Assertion failed")

docs/index.md

@@ -53,4 +53,6 @@
 
 🟢 [Longest Common Subsequence Dynamic](longest_common_subeq_dyn.md) ➔ Return the length of the longest common subsequence between two strings, or 0 if none exists
 
-🟢 [Longest Palindromic Substring](longest_palidromic_substr.md) ➔ Given a string s, return the longest palindromic substring therein
+🟢 [Longest Palindromic Substring](longest_palidromic_substr.md) ➔ Given a string s, return the longest palindromic substring therein
+
+🟢 [Interleaving String](interleave_string.md) ➔ Determine if s3 is an interleaving of s1 and s2.

docs/interleave_string.md

@@ -0,0 +1,49 @@
+### Interleaving String
+### Determine if s3 is an interleaving of s1 and s2.
+
+```python
+
+
+fn is_interleave(s1: String, s2: String, s3: String) -> Bool:
+    if len(s1) + len(s2) != len(s3):
+        return False
+    dp = List[List[Bool]](
+        length=len(s1) + 1, fill=List[Bool](length=len(s2) + 1, fill=False)
+    )
+    dp[len(s1)][len(s2)] = True
+    for i in range(len(s1), -1, -1):
+        for j in range(len(s2), -1, -1):
+            if i < len(s1) and s1[i] == s3[i + j] and dp[i + 1][j]:
+                dp[i][j] = True
+            if j < len(s2) and s2[j] == s3[i + j] and dp[i][j + 1]:
+                dp[i][j] = True
+
+    return dp[0][0]
+
+
+from testing import assert_true, assert_false
+
+
+fn main() raises:
+    var s1: String = "aabcc"
+    var s2: String = "dbbca"
+    var s3: String = "aadbbcbcac"
+    result = is_interleave(s1, s2, s3)
+    assert_true(result, "Assertion failed")
+
+    s1 = "aabcc"
+    s2 = "dbbca"
+    s3 = "aadbbbaccc"
+    result = is_interleave(s1, s2, s3)
+    assert_false(result, "Assertion failed")
+
+    s1 = ""
+    s2 = ""
+    s3 = ""
+    result = is_interleave(s1, s2, s3)
+    assert_true(result, "Assertion failed")
+
+```
+
+
+[Source](https://github.com/ratulb/mojo_programming/blob/main/codes/interleave_string.mojo)