#468 First Bad Version

You have multiple versions of a program, each numbered sequentially (starting from 0). Write a function that finds the first bad version given an isBad(version) predicate.

Key Constraints

1. All versions after the first bad version are also bad.
2. Input versions are non-negative integers.
3. If no bad version exists, return -1.
4. Use binary search for optimal O(log n) performance.

Signature

function firstBadVersion(isBad: (version: number) => boolean): (n: number) => number

The function returns another function that, given the total number of versions n, returns the first bad version index (or -1).

Example

const isBad = (v) => v >= 4;  // version 4 and later are bad
const findFirst = firstBadVersion(isBad);

findFirst(10);  // returns 4
findFirst(3);   // returns -1 (no bad versions)