Confusion on binary search and please help me

  • 1

    I have been struggling on binary search for a long time. I read many materials trying to figure out a "correct" way to write binary search code in different situations. Unfortunately, I still can not write it correctly at a very short time. My things is like this, for example, this problem, the most voted post is like :

    int findMin(vector<int> &num) {
    int lo = 0;
    int hi = num.size() - 1;
    int mid = 0;

        while(lo < hi) {
            mid = lo + (hi - lo) / 2;
            if (num[mid] > num[hi]) {
                lo = mid + 1;
            else if (num[mid] < num[hi]) {
                hi = mid;
            else { // when num[mid] and num[hi] are same
        return num[lo];

    My confusions are, how to set the loop test condition low < hi or lo <= hi and how to shrink the search space, by mid + 1 or by mid. I see some people using combinations of these two. But every time I write my own code, either I miss the answer in shrinking (maybe should use lo = mid instead of lo = mid + 1) or I got TLE since the loop wont terminate(may be should let lo = mid + 1 instead of lo = mid, since mid + 1 decreased the search space by at least one, which will finally terminates the loop).

    Any help would be appriciated!

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