added problem: string location

sorting_and_searching/string_location.py

@@ -0,0 +1,45 @@
+"""
+Given a sorted array of strings which is interspersed with empty strings, write a method to find the location of
+a given string.
+"""
+
+# @param string str the string to be located
+# @param string str_lst list of strings interspersed with empty strings
+def find_string_location(str, str_lst, start, end):
+    if start > end or not str_lst or not str:
+        return -1
+
+    middle = (start + end) / 2
+
+    middle_str = str_lst[middle]
+    if middle_str == "":
+        left = middle - 1
+        right = middle + 1
+
+        while True:
+            if left < start and right > end:
+                return -1
+
+            if left >= start and str_lst[left] != "":
+                middle = left
+                break
+            elif right <= end and str_lst[right] != "":
+                middle = right
+                break
+
+            left = left - 1
+            right = right + 1
+
+    if str_lst[middle] == str:
+        return middle
+    elif str > middle_str:
+        return find_string_location(str, str_lst, middle+1, end)
+    elif str < middle_str:
+        return find_string_location(str, str_lst, start, middle-1)
+
+if __name__ == "__main__":
+    assert find_string_location("danger", ["apple", "", "", "danger", "edible", "viscous", "", "zip"], 0, 7) == 3
+    assert find_string_location("apple", ["apple", "", "", "danger", "edible", "viscous", "", "zip"], 0, 7) == 0
+    assert find_string_location("zip", ["apple", "", "", "danger", "edible", "viscous", "", "zip"], 0, 7) == 7
+    assert find_string_location("", ["apple", "", "", "danger", "edible", "viscous", "", "zip"], 0, 7) == -1
+    print "All test cases passed successfully."