0278-first-bad-version

278. First Bad Version

Problem

Detail instruction can be found here.

Solution

public int firstBadVersion(int n) {
    int lo = 1, hi = n;
    int ans = -1;
    while (lo <= hi) {
        int mid = lo + (hi - lo) / 2;
        if (isBadVersion(mid)) {
            ans = mid;
            hi = mid - 1;
        } else 
            lo = mid + 1;
    }
    return ans;
}

Test

Compile with javac Solution.java and run with java -ea Solution.

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