add simplestl std::unordered_map

[whyb]

simplestl std::unordered_map

online compiler : https://coliru.stacked-crooked.com/a/a6c633f30aaed522

test code:

std::unordered_map<int, int> map1;
map1.insert(std::make_pair(1, 21));
map1.insert(std::make_pair(0, 10));
map1[0] = 20;
map1.erase(1);
map1.emplace(1, 11);
map1.insert(std::make_pair(2, 12));
map1.emplace(3, 13);

printf("map1 key %d has value %d\n", 0, map1.at(0));
printf("map1 key %d has value %d\n", 2, map1[2]);
printf("map1 size is %ld\n", map1.size());
printf("map1 is empty %s\n", map1.empty() ? "True" : "False");

map1.clear();

[tencent-adm]

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