170

Author: RealHacker

167_two_sum_ii/problem.txt

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+Given an array of integers that is already sorted in ascending order, find two numbers such that they add up to a specific target number.
+
+The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.
+
+You may assume that each input would have exactly one solution.
+
+Input: numbers={2, 7, 11, 15}, target=9
+Output: index1=1, index2=2

167_two_sum_ii/two_sum_ii.py

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+class Solution(object):
+    def twoSum(self, numbers, target):
+        """
+        :type numbers: List[int]
+        :type target: int
+        :rtype: List[int]
+        """
+        if len(numbers)<2:return []
+        start = 0
+        end = len(numbers)-1
+        
+        while True:
+            n = numbers[start]+numbers[end]
+            if n==target:
+                return [start+1, end+1]
+            elif n<target:
+                start+=1
+            else:
+                end-=1
+            if start==end:
+                return []
+        

170_two_sum_iii/problem.txt

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+Design and implement a TwoSum class. It should support the following operations: add and find.
+
+add - Add the number to an internal data structure.
+find - Find if there exists any pair of numbers which sum is equal to the value.
+
+For example,
+add(1); add(3); add(5);
+find(4) -> true
+find(7) -> false

170_two_sum_iii/two_sum_iii.py

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+from collections import defaultdict
+class TwoSum(object):
+
+    def __init__(self):
+        """
+        initialize your data structure here
+        """
+        self.numbers = defaultdict(int)
+
+    def add(self, number):
+        """
+        Add the number to an internal data structure.
+        :rtype: nothing
+        """
+        self.numbers[number]+=1
+
+    def find(self, value):
+        """
+        Find if there exists any pair of numbers which sum is equal to the value.
+        :type value: int
+        :rtype: bool
+        """
+        for n in self.numbers:
+            m = value-n
+            if m!=n and m in self.numbers:
+                return True
+            if m==n and self.numbers[n]>1:
+                return True
+        return False
+                
+
+# Your TwoSum object will be instantiated and called as such:
+# twoSum = TwoSum()
+# twoSum.add(number)
+# twoSum.find(value)