Hash map in Python
Hash map is simply a dictionary in Python.
Sample Code
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| # Define dictionary
indices = {}
nums = [3, 4, 5, 6]
for i, n in enumerate(nums):
indices[n] = i
for i, n in enumerate(nums):
diff = target - n
if diff in indices and indices[diff] != i:
return [i, indices[diff]]
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Hash Map in C++
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| #include <unordered_map>
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2. Define
There needs to be two values:
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| unordered_map<int, int> hashMap;
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You have to pre-define each type of key and pair of the dictionary, unlike dictionary in Python:
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| // It has string as its value
unordered_map<int, string> hashStrMap;
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3. Sample code
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| class Solution {
public:
vector<int> twoSum(vector<int>& nums, int target) {
int n = nums.size();
unordered_map<int, int> indices;
for (int i = 0; i < n; i++) {
indices[nums[i]] = i;
}
for (int i = 0; i < nums.size(); i++) {
int diff = target - nums[i];
if (indices.count(diff) && indices[diff] != i) {
return {i, indices[diff]};
}
}
}
};
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Map Comparison Table (Python vs. C++)
| Python | C++ |
| - | #include <unordered_map> |
hashMap = {} | unordered_map<int, int> hashMap; |
hashMap[1] = 3 | hashMap[1] = 3; myMap.insert({1, 1}); |
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Set in Python
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| def hasDuplicate(self, nums: List[int]) -> bool:
setDup = set()
for n in nums:
if n in setDup:
return True
else:
setDup.add(n)
return False
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Set in C++
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| bool hasDuplicate(vector<int>& nums) {
unordered_set<int> uset;
for (int i: nums) {
if (uset.find(i) != uset.end()) {
return true;
}
else {
uset.insert(i);
}
}
return false;
}
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Set Comparison Table (Python vs. C++)
| Python | C++ |
| - | #include <unordered_set> |
hashSet = set() | unordered_set<int> hashSet; |
hashSet.add(3) | hashSet.insert(3); |