leetcode2311. Longest binary subsequence less than or equal to K (medium, weekly)

Ideas ： greedy
Specific details ： Want to find less than k The youngest sequence of , Therefore, the thought is to supplement as much as possible in the front 0, Greedy thoughts , hypothesis k Yes m position , Take the last m position /m-1 position , Plus all the previous 0, That is to say ans

class Solution {
    
public:
    int longestSubsequence(string s, int k) {
    
 
        int bits = 32 - __builtin_clz(k), n = s.size();
        if (n < bits) return n;
        int m = bits - 1;
        string tmp = s.substr(n - bits);
        if (stoi(tmp, nullptr, 2) <= k) m = bits;
        return m + count_if(s.begin(), s.end() - m, [](char ch){
    return ch == '0';});
    }
};

Code difficulties ：string Turn according to binary int ：stoi(s, nullptr, 2)