Yale does not admit by major. Indeed, no Ivy League university admits by major (excluding certain schools within Cornell that are irrelevant to your question). Ivy League universities with multiple undergraduate achools - Penn, Columbia, Cornell - admit by school, although don’t necessarily share acceptance rates by school.
As to which is the easiest to get into? Easy is relative; all are difficult. But you can answer your own question by researching acceptance rates.
That said, not all Ivy League schools have A+ CS undergrad programs and there are many unis with better programs than some Ivy League schools.