30 Days of Code [Day 23]

05 Sep 2021

QUESTION : 278. First Bad Version

// The API isBadVersion is defined for you.
// bool isBadVersion(int version);

#define vi vector<int>
#define pii pair<int, int>
#define pb push_back
#define mp make_pair
#define all(v) v.begin(), v.end()
#define fo(i,s,n) for(int i=s;i<n;++i)
#define of(i,s,n) for(int i=s-1;i>=n;--i)
#define fv(V) for( auto &it : V )
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
class Solution {
public:
    int firstBadVersion(int n) {
        int l = 0;
        int r = n;
        int res = 0;
        while(l <= r){
            int mid = l + (r-l)/2;
            if(!isBadVersion(mid)){
                l = mid + 1;
            }
            else{
                res = mid;
                r = mid-1;
            }
        }
        return res;
    }
};