Issue with leet code problem 3 Longest substring [closed] - c++

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Essentially we are asked to find, given a string, the longest substring with no repeating characters, below I am using the sliding window approach.
Examples:
Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.
Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.
Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.
My attempt:
class Solution {
public:
int lengthOfLongestSubstring(std::string s){
int count{0};
std::map<char,int> char_map;
std::vector<char> char_vec;
auto left{char_vec.begin()};
auto right{char_vec.begin()};
for(int i = 0; i < s.length(); i++){
char_vec.push_back(s[i]);
if(char_map.find(s[i]) != char_map.end()){
char_map[s[i]]++;
}
else{
char_map.insert(std::pair<char,int>{s[i],1});
}
while(++right != char_vec.end() && char_map[*(right)] > 1){
char_map[*(left++)]--;
}
count = (count < std::distance(left,right)) ? std::distance(left,right) : count;
}
return count;
}
};
However, there is an issue in the while loop near the end of the code block that is causing
compiler error and am very confused about how to solve it.

Answer 1

So your code is suffering from iterator invalidation. Here you have a vector
std::vector<char> char_vec;
and here you create two iterators to that vector
auto left{char_vec.begin()};
auto right{char_vec.begin()};
and then here you add an item to that vector
char_vec.push_back(s[i]);
When you add an item to a vector you may invalidate any iterators to that vector, and any use of such iterators causes your program to have undefined behaviour.
Instead of using iterators you could try using offsets (i.e. integer variables which you use to index the vector). These have the advantage that they are not invalidated as the vector grows.
For more information on iterator invalidation see the table on this page. Different containers have different behaviour wrt iterator invalidation.