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1 描述
Description
Create a timebased key-value store class TimeMap, that supports two operations.
- set(string key, string value, int timestamp)
Stores the key and value, along with the given timestamp.
- get(string key, int timestamp)
Returns a value such that set(key, value, timestamp_prev) was called previously, with timestamp_prev <= timestamp.
- If there are multiple such values, it returns the one with the largest timestamp_prev.
- If there are no values, it returns the empty string ("").
Example 1
- Input: inputs = [“TimeMap”,“set”,“get”,“get”,“set”,“get”,“get”], inputs = [[],[“foo”,“bar”,1],[“foo”,1],[“foo”,3],[“foo”,“bar2”,4],[“foo”,4],[“foo”,5]]
- Output: [null,null,“bar”,“bar”,null,“bar2”,“bar2”]
- Explanation:
TimeMap kv;
kv.set(“foo”, “bar”, 1); // store the key “foo” and value “bar” along with timestamp = 1
kv.get(“foo”, 1); // output “bar”
kv.get(“foo”, 3); // output “bar” since there is no value corresponding to foo at timestamp 3 and timestamp 2, then the only value is at timestamp 1 ie “bar”
kv.set(“foo”, “bar2”, 4);
kv.get(“foo”, 4); // output “bar2”
kv.get(“foo”, 5); //output “bar2”
Example 2
- Input: inputs = [“TimeMap”,“set”,“set”,“get”,“get”,“get”,“get”,“get”], inputs = [[],[“love”,“high”,10],[“love”,“low”,20],[“love”,5],[“love”,10],[“love”,15],[“love”,20],[“love”,25]]
- Output: [null,null,null,"",“high”,“high”,“low”,“low”]
Note
- All key/value strings are lowercase.
- All key/value strings have length in the range [1, 100]
- The timestamps for all TimeMap.set operations are strictly increasing.
- 1 <= timestamp <= 10^7
- TimeMap.set and TimeMap.get functions will be called a total of 120000 times (combined) per test case.
2 代码
#include <iostream>
#include <string>
#include <vector>
#include <unordered_map>
#include <algorithm>
using namespace std;
class TimeMap {
public:
unordered_map<string, vector<pair<int, string>>> k_vTime;
TimeMap() {
}
void set(string key, string value, int timestamp) {
pair<int, string> vTime(timestamp, value);
k_vTime[key].push_back(vTime);
}
string get(string key, int timestamp) {
string res = "";
vector<pair<int, string>>& vTimes = k_vTime[key];
auto it = upper_bound(vTimes.begin(), vTimes.end(), pair<int, string>(timestamp,""),
[&](pair<int, string> a, pair<int, string> b) {return a.first < b.first; });
if (it != vTimes.begin())
{
it--;
res = it->second;
}
return res;
}
};
int main()
{
TimeMap kv;
kv.set("foo", "bar", 1);
cout << kv.get("foo", 1) << endl;
cout << kv.get("foo", 3) << endl;
kv.set("foo", "bar2", 4);
cout << kv.get("foo", 4) << endl;
cout << kv.get("foo", 5) << endl;
system("pause");
return 0;
}
//输出
bar
bar
bar2
bar2