I have a program in which I am using an iterator to get access to a value of a map entry .
#include <iostream>
#include <cstdio>
#include <unordered_map>
#include <utility>
#include <algorithm>
using namespace std;
int main()
{
int a[]={1,2,4,7,9,3,3,55,66,88,11};
int k = 58;
unordered_map<int,int> c;
int i=0;
for(auto x: a)
{
c.insert(make_pair(x,i));
i++;
}
for(auto x: c)
{
if(c.count(k-x.first)==1) printf("%d %d\n",x.second,(c.find(k-x))->second);
}
}
In the line:
if(c.count(k-x.first)==1) printf("%d %d\n",x.second,(c.find(k-x))->second);
I am getting errors especially in c.find()->second
. I think it is the way to access elements from the iterator. What is wrong?
You cannot say
c.find(k-x)
Because k
is an int
and x
is a std::pair<int, int>
. Do you mean one of these two?
c.find(k - x.first)
Or
c.find(k - x.second)
As a side note, it is generally unsafe to directly derefernce the returned iterator from find
because if find
returns .end()
(as in, it didn't find an element with that key) then you've got a problem.
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.