TheAlgorithms-C/leetcode/src/278.c

// Forward declaration of isBadVersion API.
bool isBadVersion(int version);

int firstBadVersion(int n) {
    int low = 1, high = n;
    while (low <= high) {
        int mid = low + (high - low) / 2;
        if(isBadVersion(mid)) {
            high = mid - 1;
        } else {
            low = mid + 1;
        }
    }
    return low;
}