pancakeRouter.sol

function _swap(uint[] memory amounts, address[] memory path, address _to) internal virtual {
    for (uint i; i < path.length - 1; i++) {
        (address input, address output) = (path[i], path[i + 1]);
        (address token0,) = PancakeLibrary.sortTokens(input, output);
        uint amountOut = amounts[i + 1];
        (uint amount0Out, uint amount1Out) = input == token0 ? (uint(0), amountOut) : (amountOut, uint(0));
        address to = i < path.length - 2 ? PancakeLibrary.pairFor(factory, output, path[i + 2]) : _to;
        IPancakePair(PancakeLibrary.pairFor(factory, input, output)).swap(
            amount0Out, amount1Out, to, new bytes(0)
        );
    }
}