Implement a MapSum class with insert
, and sum
methods.
For the method insert
, you'll be given a pair of (string, integer). The string represents the key and the integer represents the value. If the key already existed, then the original key-value pair will be overridden to the new one.
For the method sum
, you'll be given a string representing the prefix, and you need to return the sum of all the pairs' value whose key starts with the prefix.
Example 1:
Input: insert("apple", 3), Output: Null Input: sum("ap"), Output: 3 Input: insert("app", 2), Output: Null Input: sum("ap"), Output: 5
class MapSum { map<string, int> mp; public: /** Initialize your data structure here. */ MapSum() {} void insert(string key, int val) { mp[key]=val; } int sum(string prefix) { /* if (mp.find(prefix)==mp.end()){ return 0; } */ int res=0, n=prefix.size(); for(auto iter=mp.lower_bound(prefix);iter!=mp.end();++iter) { if(iter->first.substr(0,n)!=prefix) break; res+=iter->second; } return res; } }; /** * Your MapSum object will be instantiated and called as such: * MapSum obj = new MapSum(); * obj.insert(key,val); * int param_2 = obj.sum(prefix); */
c++ map lower_bound upper_bound用法
运行 https://www.cnblogs.com/billin/archive/2011/09/01/2162102.html 一下代码就知道了
#include<map> #include<iostream> int main() { using namespace std; map<int,int> m1; map<int,int>::const_iterator m1_AcIter,m1_RcIter; typedef pair<int,int> Int_Pair; m1.insert(Int_Pair(1,10)); m1.insert(Int_Pair(2,20)); m1.insert(Int_Pair(3,30)); m1_RcIter=m1.lower_bound(2); cout<<"The first elem of map m1 with a key greater than 2 is: " <<m1_RcIter->second<<"."<<endl; m1_RcIter=m1.lower_bound(4); if(m1_RcIter==m1.end()) { cout<<"The map m1 doesn't have an element with a key of 4."<<endl; } else { cout<<"The element of map m1 with a key of 4 is: "<<m1_RcIter->second<<"."<<endl; } m1_AcIter=m1.end(); m1_AcIter--; m1_RcIter=m1.lower_bound(m1_AcIter->first); cout<<"The element of m1 with a key mathing the last element is: " <<m1_RcIter->second<<"."<<endl; return 1; }
输出
python代码
class MapSum(object): def __init__(self): """ Initialize your data structure here. """ self.d={} def insert(self, key, val): """ :type key: str :type val: int :rtype: void """ self.d[key]=val def sum(self, prefix): """ :type prefix: str :rtype: int """ return sum(self.d[i] for i in self.d if i.startswith(prefix)) # Your MapSum object will be instantiated and called as such: # obj = MapSum() # obj.insert(key,val) # param_2 = obj.sum(prefix)