What is the best wood for outdoor flooring in location with high humidity levels?

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Cedar, Redwood, or Cork.

It depends on what you mean by "location." If you mean you live in a region where there's a lot of humidity, then you want to go for a very hard wood, like maple. Maple is extremely hard, can take a lot of abuse, is about as impervious to water as wood can be, and expands and contracts very little due to humidity.

If you mean the floor is going to be somewhere in the house that gets high humidity, like a basement, then the only hardwood floor I'd recommend is bamboo, although that's not really wood. It looks a lot like wood, actually a lot like maple. Bamboo floors are super hard, super durable, and can survive even being flooded and soaked in water without buckling or warping. Bamboo costs a little more than maple, but they look great.

Whatever you do, don't go with laminate floors, floors where it's actually just a thin wood veneer or even faux wood over a melamine resin. They are not for humidity. They get ruined even by a little moisture because that melamine resin sucks up liquid like a sponge and then expands but never shrinks back down so that you end up with all the edges and corners of each board coming up and the floor heaving and buckling. That stuff is only for upstairs bedrooms and areas that rarely to never get exposed to moisture, where that's not even really a possibility.

Treated lumber.