SEOUL—Samsung Electronics Co. Ltd. reported on Thursday an estimated 50 percent jump in quarterly operating earnings to post its highest first-quarter profit since 2018, beating expectations as solid demand underpinned prices for memory chips. Earnings at the world’s largest memory chip and smartphone maker were also supported by brisk smartphone sales in the quarter, along with a disruption at a rival NAND Flash chip plant, analysts said. Samsung put its first-quarter profit at 14.1 trillion won ($11.6 billion) in a preliminary earnings release, versus a Refinitiv SmartEstimate of 13.3 trillion won. Revenue likely rose 18 percent from the same period a year earlier to a record 77 trillion won, also above market expectations. “The guidance beat market expectations, probably due to memory chip shipments and prices being better than expected,” said Park Sung-soon, analyst at Cape Investment & Securities. Although memory chip prices dipped in the first quarter, analysts said …