two leetcode problems

Author: springuper

longestCommonPrefix.py

@@ -0,0 +1,32 @@
+ # @return a string
+def longestCommonPrefix(strs):
+    l = len(strs)
+    if l == 0:
+        return ''
+    elif l == 1:
+        return strs[0]
+    prefix = ''
+    a = strs[0]
+    b = strs[1]
+    lb = len(b)
+    for i in range(len(a)):
+        if i >= lb or a[i] != b[i]:
+            break
+        prefix += a[i]
+    if prefix == '':
+        return ''
+
+    for i in range(2, len(strs)):
+        s = strs[i]
+        ls = len(s)
+        for i in range(len(prefix)):
+            if i >= ls or s[i] != prefix[i]:
+                prefix = prefix[0:i]
+                break
+
+    return prefix
+
+assert longestCommonPrefix([]) == ''
+assert longestCommonPrefix(['a', 'b']) == ''
+assert longestCommonPrefix(['abc', 'ab']) == 'ab'
+assert longestCommonPrefix(['abc', 'abcd', 'abd']) == 'ab'

validParentheses.py

@@ -0,0 +1,29 @@
+# @return a boolean
+def isValid(s):
+    stack = []
+    l = 0
+    if len(s) % 2 == 1:
+        return False
+    for cha in s:
+        if cha == '(' or cha == '[' or cha == '{':
+            stack.append(cha)
+            l += 1
+        else:
+            if l == 0:
+                return False
+            if cha == ')' and stack[-1] != '(':
+                return False
+            elif cha == ']' and stack[-1] != '[':
+                return False
+            elif cha == '}' and stack[-1] != '{':
+                return False
+            stack.pop()
+            l -= 1
+    return l == 0
+
+
+assert isValid('()') == True
+assert isValid('(') == False
+assert isValid('()[]{}') == True
+assert isValid('([])') == True
+assert isValid('([)]') == False