First value at least target

In a sorted array, find the first index whose value is at least the target. This is also where the target would be inserted.

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def lower_bound(nums, target):
    lo, hi, ans = 0, len(nums) - 1, len(nums)
    while lo <= hi:
        mid = (lo + hi) // 2
        if nums[mid] >= target:
            ans = mid; hi = mid - 1
        else:
            lo = mid + 1
    return ans