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[LeetCode] 170. Two Sum III - Data structure design 两数之和之三 - 数据结构设计
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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
Two Sum题的拓展，设计一个数据结构，实现添加数字和找目标数字的功能。用HashMap来存数字和查找。
Java:
public class TwoSum {
private HashMap<Integer, Integer> elements = new HashMap<Integer, Integer>();
public void add(int number) {
if (elements.containsKey(number)) {
elements.put(number, elements.get(number) + 1);
} else {
elements.put(number, 1);
}
}
public boolean find(int value) {
for (Integer i : elements.keySet()) {
int target = value - i;
if (elements.containsKey(target)) {
if (i == target && elements.get(target) < 2) {
continue;
}
return true;
}
}
return false;
}
}
Python:
class TwoSum(object):
def __init__(self):
self.dic = {}
def add(self, number):
if number not in self.dic:
self.dic[number] = 1
else:
self.dic[number] += 1
def find(self, value):
dic = self.dic
for num in dic:
if value - num in dic and (value - num != num or dic[num] > 1):
return True
return False
Python:
class TwoSum(object):
def __init__(self):
self.lookup = defaultdict(int)
def add(self, number):
self.lookup[number] += 1
def find(self, value):
for key in self.lookup:
num = value - key
if num in self.lookup and (num != key or self.lookup[key] > 1):
return True
return False
C++:
class TwoSum {
public:
void add(int number) {
++m[number];
}
bool find(int value) {
for (auto a : m) {
int t = value - a.first;
if ((t != a.first && m.count(t)) || (t == a.first && a.second > 1)) {
return true;
}
}
return false;
}
private:
unordered_map<int, int> m;
};
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